BIOLOGY LIBRARY UCB
Scales of Beetles and Fishes.
Frontispiece.
1. Weevil, natural size. 2. Scales of Weevil, magnified 100 diameters.
3. Scales of Green Weevil, magnified 150 diameters. 4. Scale of Perch, magnified 4 diameters. 5. Lines on Perch's scale, magnified 100 diameters. 6. Scale of Sole, magnified 9 diameters.
7. Piece of Eel's Skin, magnified 4 diameters. 8. Upper and under layers of Eel-skin, and Eel scales. 9. Scale of Eel, magnified 50 diameter*.
OBJECTS
FOR THE
MICROSCOPE
A POPULAR DESCRIPTION OF THE MOST
INSTRUCTIVE AND BEAUTIFUL SUBJECTS FOR
EXHIBITION OR EXAMINATION.
BY L. LANE C L A K K E.
EIGHTH EDITION. ILLUSTRATED WITH COLOURED PLATES.
LONDON :
GKOOMBKIJjGE AND SONS. 1889.
SIMSON, PRINTER, HERTFORD.
CONTENTS.
ON THE USE OF THE MICROSCOPE.
PAGE Directions for Mounting Objects ... ... ... ... ... 6
„ ,, Mounting in Balsam... ... ... ... ... 7
PART I.
OBJECTS FROM THE VEGETABLE KINGDOM.
CHAPTER I.
Shapes of Cells— (Jell-contents— Oil Cells— Hairs of Plants- Cuticle and Stomata — Cuticle of Yucca, of Aloe, of Deutzia Scabra, of Amaryllis, of Ind'an Corn, of Saccalobium, of Elseagnus, of Tillandsia, of Onosma, of Opuntia ... .. 9
Rawhides. — Cuticle of Hyacinth — Raphides from Rhubarb — Anagallis— Spiral fibre— Spiral Cells of Oucidium — Spiral Vessels of Collomia— Spiral Cells of Balsam —Spiral Cells of Sphagnum -Scalar if orm Vessels ... ... ... ... 19
Pollen — Pollen of Mallow, of Hollyhock, of Passion -flower, of CEnothera — A few words more on the Pollen — Pollen-tubes -Stamens ... 23
Seeds. —Poppy — Sweet-William— Silene, or Stellaria — Orchis —
Eccremocarpus or Calarnpelis ... ... ... ... ... 28
CHAPTER II.
SECTIONS OF WOOD.
Ruscus— Whanghae Cane— Asparagus— Section of Hazel, of Pine, of Yew — Cedar of Lebanon — Vegetable Ivory — Fossil Coni- ferous Wood — Pine Wood — Section of Cocoa-nut, of Cob-nut, of Snake-wood ... ... — ... ... ... ... 29
Moss.— Slides of Dicranum, Funaria, Etc., Etc.— Spore-cases of Fern — Elaters of Equisetum — Elaters of Jungermannia — Junger- mannia Bidentata . ... ... ... ... ... ... 32
Fungi. — Slide of Puccinia, or Phragmidium — Blight of Wheat
(Smut) — U redo Foetida, or Bunt— U redo, or ^Ecidium ... 39
JV CONTENTS.
CHAPTER III.
INFUSORIAL EARTHS.
PACK
Diatoms of Gu:\no— Naviculse— Navicula Hippocarapa -Pleuro sigina — Meloseira — Meloseira Borreri — Achnanthes Longipes, — Synedra Ulna — Bacillariae— Gomphonema— Licmophora — Rhabdonema — Grain matophora Marina — Biddulphia — Am- phitetras — Isthima Obliqua— Arachnoidiscus — Heliopelta — Actinocyclus — Asteromphalus Astetolampra — Coscinodiscus 42
Desmidiacece.— Volvox Globator — Closterium — Confervae — Zyg-
nema — Achyla Prolifera... ... ... ... ••• ••• 50
PART II.
OBJECTS FROM THE ANIMAL KINGDOM.
CHAPTER I.
OBJECTS FROM THE AKACHNIDA.
Spider's Foot — Spider's Legs — Spider's Spinnarets — Spider's
Eyes — Spider's Jaws — Spider's Palpi — Epidermis of Spider 57
CHAPTER II.
INSECT PARTS.
Tongues of Insects. —Tongue or Proboscis of Hive Bee— Tongue of Wasp — Butterfly's Tongue or Proboscis — Proboscis or Tongue of Blow-flv— Proboscis of Tabanus, of Gnat, of Empis-fly, of Dioctria— Head of Conops, of Rhingia, or Syrphus, of Drone fly, or Heliophilus, of Eristalis, of Tipula, of Lira- nobia, of Hemerobious, of Panorpa— Tongue of Cricket — Gizzard of Cricket — Mouth of Soldier-beetle, Calathus Castel- loides, of Brachinus, of Onthophagus, of Anchomenus, of Crioceris, of Ladybird, of Stenopterus Rufus .. ... ... 64
Antennce. — Antennae of Cockchafer, of Nitidularia. of Hydrophilus, of Elater, of Syrphus, of Blow-fly, of Bee, of Ichneumon, of Argynnis — Palpi of Argynnis — Antennae of Dragon-fly, of Silkworm-moth 79
Spirccdes and Trachece. — Spiracles of Dytiscus — Trahese of Dy- tiscus- -Spiracles of Cockchafer, of Fly, of Tipula, of Water Larvae — Aerating Leaflet of Libellula — Abdomen of Ephe- mera, or Spiracles ... ... ... ... ... ... 83
CONTENTS.
PAGE
Circulation of Blood 85
Spiracles of Larva of Bot-fly 86
Wings of Insects. — Wing of Scatophaga, of House-fly, of Blue- bottle-fly, of Syrphus, of Midge, of Gnat, of Beetle, of Cricket 86
Scales of Insects. — Scales of Morpho Menelaus, of Polyommatus Argus, of Hipparchia Janira, of Pontia Brasscia, of Silkworm- moth, of Clothes moth, of Podur.i, of Lepisma Saccharina ... 91
Elytra of Diamond Beetle 94
Feet of Insects. — Foot of Syrphus— Leg of Dytncus, or Dyticus — Foot of Wasp, of Ophion, Leg of Bee, of Gyrinus, of Bra- chinus, of Anchomenus, of Calathm Castelloides — Sting of Wasp and Bee, of Gnat, of Tabanus . .. 94
Egg of Bot-fly, or CEstrus 98
CHAPTER I [I.
INSECTS MOUNTED WHOLE.
The Telephorus, or Soldier-beetle — Helphorus Granularis -
Catheretes Urticse — Coccinella, or Lady-bird ... ... 100
ffemiptera. — Velia Rivulorum— Notonecta, or the Water Boatman — Reduvius. or Bed-bug — Cimex, or Field-bug — Aphis — Aphrophora, or Cuckoo -spit — Thrips ... ... 106
Hymenoptera. — Tenthredo, or Saw-fly — Cypheus Pygmaaus — Ihc- neumon-fly — Microgaster Glomeratus — Aphldius ,'Avenae — Ephedrus Plagiator — Ceraphron Carpenterii — Chelymorpha Phyllophora, or the Turtle-snap 3d Leaf-bearer ... ... HO
CHAPTER IV.
DIPTEBA. Culex Pipiens ... ... ... ... ... ... ... ... 120
Ptychoptera ... ... ... ... ... ... 124
Scatophaga.— The family of the Brachycera— the Scatophaga — Lonchoptera — Bibeo — Dolichopus — The Opotnyza — Uhlorops — Phoro — Leptis — Asilus — Empis — Empis Stercorea — Hilara— Syrphus Pyrastri — Borborus Equinus — Sepedon— Sepsis 125
The Halteres, Poiscrs, of Diptera. —Halter QS of Blow-fly— Hal-
teres of Tabanus ... ... .. ... ... ... . 143
VJ CONTENTS.
CHAPTER V.
PARASITES
PAGE
The Flea. — The Pygidium of a Flea .. ... ... .. ... 144
Pediculus, or Lome ........ 143
The Acari, or Tics, Mites.— Acarus Domesticus, or Common Cheese-mites — Acarus Passularum — Acarus Passerinus — Ixodes, or Dog-tick — Melophagus — Stenopteryx — Ornitho- rayia — Nycteribia— Chlifer— Acarus Ga-nasus — Trombidium Phalangii — Trombidium Autumnale —Water-mites — Entozoa 147
CHAPTER VI.
MICROSCOPIC MOTHS.
Nepticula Aurella— Nepticula MaKelli— Nepticula Prunatori— Nepticula Trimaculella — Ceriastoma— Scitella — Lithocolletis Sylve'la — Lithocolletis Schreberella — Lithocolletis Trifas- ciella— Lithocolletis Hortella— Gracilaria Swederella— Gra- cilaria Syringella — Coleophora Gryphipennella — Ornix Guttea— Lithocolletis Scabiosella— Glyphipteryx Thrasonella — Head of Ochsenheimeria, &c. . ... ... ... ... 153
CHAPTER VII.
PALATES.
Palate of Helix Pomatia— Helix Aspersa — Limax — Helix Hor- teusis — Helix Nemoralis— Helix Rufescens — Helix Vigata — Zonites, or Helix Nitida — Palate of Whelk, of Purpurea, of Nasa, of Trochua Ziziph'mus, of Trochus Crassus, of Trochus Umbilicatus, of Periwinkle, of Haliotis, or Aumer, of Pleurobranch, of Aplysia, of Doris, of Limpet, of Chiton, of Yellow Nerite, of Neritina Fluviatilis, of Lyraneus Stag- nalis, of Planorbis Cornea, of Paludina, of Cyclastoma ... 158
CHAPTER VIII.
SLIDES OF ZOOPHYTES.
A nthoza.— Sertularu Pumila— Sertularia Polyzonias— Se rtularia Operculata — Sertularia Uosacea — Liomedea Geniculata — Laomedea Dichotomy — Plumularia Cristata — Plumularia Falcata 167
Polyzoa. — Gemicellaria — Gemmellaria Loriculata — Gemecelari.*, or Notouiia Bursana — (Jellularia Avioularia — Flustra Trun- cata — Pustulipora Fossil — Flustra Chartaceee — Cellularia Reptans — Cellularia Ciliata — Crisea Eburnea — Crisea Cornuta — Serialaria Lendigera — Fresh-water Zoophytes ... ... 171
CONTENTS. vii
CHAPTER IX.
SEA-WKEDS— MARINE ALG.E.
PAGE
Marine Algse-Callithamnion — Cerarnium— Ptilota Plumosa— Plocamium Vulgare, Coccineum — Polysiphonia — Spheio- coccus — Griffithsia — Gracillaria — Laurentia — Odonthalia — Bonnemaisonnia — Delesseria — Rhodomela — Spyridia Fila- mentosa — Chaetospora Wiggii — Halymenia — Dasya — Dasya Arbuscula — Dasya Occellata — Dasya Venusta — Goadby's Solution for Marine Algse 181
CHAPTER X.
FOBAMINATED SHELLS.
The Operculina— Fossil Foraminated Shells from Barbadoes —
Orbitolites — Nummulites ... 194
CHAPTER XI.
8PICULES OP SPONGES.
Spicules of Sponge — Gemmules of Pachymatisma— Spicules of
Grantia Nivea .. 193
CHAPTER XII.
SECTIONS OF BONE.
Man's Metacarpal— Fin-bone of Lepidosteos— Femur of Tetrao
Urogallus ... ... ... ... ... ... ... ... 201
Sections of Teeth. — Sections of Human Tooth ... „ ... 204 CHAPTER XIII.
HAIRS.
Human Hair — Hairs of Dormouse and Common Mouse, of Mole, of Bat, of Elephant, of' Camel, of Reindeer, of Ornitho- rhynchus, of Larva of Dermestes ... ... ... ... 206
CHAPTER XIV.
sncuLES OF HOLOTHURLI;.
Spicules of Synapta— Spicules of Chirodota— Calcareous Spicules of Doris— Calcareous Skeleton of Doris— Spicules of Gorgonia — Spicules of Alcynonium Digitatum — Section of Echinus Spine 208
Vlll CONTENTS,
OBJECTS FOR POLARISCOPE.
PAGE
Polarized Light — Selenite — Rhinoceros Horn — Whalebone — Elytra of Dytiscus— Cuticle of Deutzia Leaf— Section of Quartz— List of Objects ... 212
CHAPTER XV.
ANATOMICAL INJECTED PREPARATIONS
Liver : Human, Rabbit, Pig, Monkey— Villi, Small Intestines of Man, of Monkey, of Pig, of Tog, of Cat, of Rabbit— Duode- num of Mouse — Lung : Human, Monkey, Bear, Puppy, Pig, Cat, Sheep, Fowl, Goose, Turtle, Rattlesnake, Frog, Tortoise, — Gill of Eel— Fin of Turtle— Stomach of Mouse— Skin- Palm of Hand— Foot of Cat - Skin of Toad— Ciliary Pro- cesses—Eye of Ox— Ear of Mouse— Toe of White Mouse — Kidney — Tongue: Human, Dog, Cat, Mouse — Brain: Human, Cat, Rabbit, Mouse 216
CHAPTER XVI.
SLIDES OF CRYSTALLIZATION.
Selenite — Acetate of Copper -Sulphate of Copper— Alum— Oxa- lurate of Ammonia — Murexide, or Purpurute of Ammonia — Hydrochlorate, or Muriate of Ammonia — Oxalate of Am- monia — Salt of Brucia — lodo-disulphate of Quinine — Borax, or Bi-borate of Soda — Boracic Acid — Sulphate of Magnesia — Ammonio-Phosphates of Magnesia — Uric Acid, or Lithic Acid —Nitrate of Potash, or N itre- Saltpetre —Salicine— Nitrate of Silver ... 224
PART I.
OBJECTS FROM THE VEGETABLE KINGDOM.
" Search out the wisdom of Nature, — there is depth in all her doings. She hath on a mighty scale a general use for all things ; Yet hath she specially for each its microscopic purpose. There is use in the prisoned air that swelleth the pods of the laburnum, Design in the venomed thorns that sentinel the leaves of a nettle, A final cause for the aromatic gum that congealeth the moss around a
rose, A reason for each blade of grass that raiseth its small spine."
Proverbial Philosophy.
" On every herb on which you tread Are written words which, rightly read, Will lead you from earth's fragrant sod To hope and holiness and God." Anon.
CHAPTER I.
IN every collection of objects for the microscope we find many preparations from the vegetable world — slides of cuticles, nbro-cells, pollen-grains, raphides, &c. &c. ; and few lose more in being hastily looked at, as merely pretty objects, without that knowledge of flower-life which alone can enable us rightly to appreciate them.
If we are wholly ignorant of the structure of plants, their uses, their variety, and the secret mechanism by which their life is renewed day by day, we are apt to look at these slides for mere amusement, for the lust of the eye, pleased as a child or as a savage with strange forms or brilliant colours. Therefore, before we take them up, it will not be 'KiDrofitable to learn if we do not know, and refresh our memory if we have once known, something of the mysteries of creation in vegetable life.
10 Objects for the Microscope.
Thousands of years have passed away since angel voices sang the praises of God when He had finished the fair work of creation, and — looking upon the lowliest herb of the field as upon the birds of the air, the living creatures of the deep, wide sea, the beasts of the earth, and man, the lord of all — " behold it was very good." Thousands of years have passed away : man has changed, it may be that the lower creatures have partaken of his fall ; but of the beau- tiful flowers and the stately trees we have no reason to believe that there is aught in them that offends their Maker; we fearlessly search into the recesses of their being, and behold they are wondrously beautiful and still " very good."
A flower-plant has been likened by linger,* a German botanist, to " a most skilfully-planned chemical laboratory, a most ingenious mechanism for the display of physical forces, and one of the simplest, and consequently one of the most sublime, structures ever designed or executed."
He also likens the growth of a plant to the building of a glorious edifice ; he compares the cells of vegetable life, in their varied forms and sizes, to the stones of a building forming a kind of masonry. In some parts of a plant the cells are long, and form pipes or cylinders, or they are condensed and thickened into fibre. In the cuticle of leaf and flower we have flattened, oblong, or crenellated cells, which, as a tesselated pavement, protect the more delicate machinery within.
We find, by the help of a microscope, not only this, but also the store chambers of cell-contents where the materials for the plant edifice are collected and preserved.
Again, in the building of .a plant there are air-passages resembling regularly-shaped rooms, or romantic caves, or microscopic grottos, terminating in what are called stomata; which stomata have folding doors or valves to open or shut at pleasure, so that the air circulates freely through the plant organism. These are mostly on the under side of a leaf, so the under cuticle is the one we mount for observa-
* 'Unorer's Letters.'
Objects jor the Microscope. 1 1
tion, and we shall notice these stomata more particularly when the slides are described.
The origin of every plant is a single cell. The perfection of a plant, from the tiniest moss to the loftiest oak, is in a countless multitude of simple cells containing various sub- stances needful for its growth, and of an infinite variety of shape and substance : for some cells are very thick ; some are dotted, to allow of the circulation of air in the deep recesses of the stem ; some have variegated walls produced by its secondary deposits, like fibre coiled around, and these fibre-cells are abundant in some plants. We have them from the Oncidium and Opuntia. Some cells of spiral fibre act as trachea for breathing organs, or give lightness and elasticity to a stem. They are abundant in strawberry leaves, vine leaves, rhubarb stems, spinach, and there are beautiful examples in the slide of spiral cells from the balsam. Much more can be learnt from the examina- tion of the fresh plant, because of the difficulty of preserving cells and their contents. Is it not wonderful to think of a little plant having its store chambers secreting starch, sugar, gum, oils, raphides, colouring matter— aye, and beautiful crystals floating in the cell-fluid, or suspended, as are the cystolithes, in the cell-chambers of the nettle tribe ?
The very knowledge that such things are, and that they may be seen in an infinite variety, will lead us first to look at these slides understandingly, then to seek further by examination of living plants. This will induce us to study such books as Quekett's ' Histiology,' ' Carpenter on the Microscope,' ' Mohl on the Vegetable Cell,' ' Schacht on the Microscope,' 'Unger's Letters,' &c. &c. Then we shall see our microscope worthily, and our cabinet of objects will cease to be a mere toy.
SHAPES OF CELLS.
As the object of this little book is to excite and not to satisfy the desire of an inquiring mind, let me here suggest that it is well to prove all things ; and before you quite believe that every flower and plant is made up of single cells of varied form, exami'^ for yourself thus : — Take a
12 Objects for the Microscope.
flower, a few bits of stalk, a lily leaf, or small piece of rhubarb stalk, another of cucumber, a thin slice of raw potato, a wallflower, or a primrose — any flower : macerate it in water for a day or two, until it begins to decompose, and the smallest portion placed under the microscope with a drop of water will show you the now separating cells of various shape : those in stalks oblong or cylindrical ; those in the surface of petals and leaves square, or round, or hexagonal, or irregular, with zigzag boundaries, or papilli- form, as in the Geranium, Sweetwilliam, &c. ; those of the parenchyma or pulp of the leaf generally oval. In looking at these, you will certainly find a variety of contents which are seldom preserved for any length of time, and which you must therefore observe in the fresh and living plant.
CELL-CONTENTS.
In the slice of potato you will find every cell crowded with starch-granules, that is, if it is a good potato ; for starch is to the potato what fat is to an animal, and if it is in " good condition " the cells should be full of it. The test of this is a drop of tincture of iodine, which turns the starch- granules to a beautiful blue or violet colour ; and a diseased potato with empty cells will therefore be detected by a drop of that same iodine.
In the stem of a lily you will find starch-grains, mixed with green granules of chlorophylle, a kind of vegetable wax, which gives the green colour to leaves.
All our farinaceous plants contain abundance of starch, especially wheat, barley, oats, maize, rice, arrow-root ; and the granules differ from each other in size and form so decidedly, that they cannot well be mistaken by a careful observer. They are prepared for the microscope, and sold as polariscope objects, because the examination of a starch granule with polarized light shows it with a beautiful black cross, revolving with the polarizer ; or, if over a selenite stage, a brilliant play of colours is obtained.
Besides starch-grains and chlorophylle, you will find something else in the cells of that lily stem, which I select as an easy one to obtain in any garden. In some cells, not
Objects for the Microscope. 13
in all, you will probably observe a larger granule, with a lesser one within, or perhaps several lesser ones ; the large granule is the nucleus, the minute inner ones the nucleoli ; they are the supposed origin of new cells, and much that is exceedingly interesting has been written in the works before referred to : ' Mohl on the Vegetable Cell ; ' ' Hofineister's Die Enstehung des Embryo.' These nuclei are to be observed in pollen-grains, in the hairs of Tradescantiae, or Spiderwort, especially in the pollen of the fir-tree tribe.
OIL CELLS.
Cells containing oil are beautiful objects when found as on rose-trees, on the stem of Saxifrage, Geraniums, Col- lomia, Drasena, raised upon delicate stalks, often brightly coloured, or glittering diamond-like in the sunshine.* Some- times the oil cells are sessile, in golden spots upon the back of a black-currant leaf ; or white and silvery in the recesses of a Sage leaf, a leaf of Rue, or Hop, or Mulberry.
Sometimes these oil cells are internal, as in the rind of an orange, where they are very large and most easily ob- served ; also in the leaves of Myrtle and Magnolia, of Hypericum, St. John's wort, so common in woods and hedges : those little dark dots are the oil cells, and trans- parent, if you hold the leaf up against the light, and examine it with a pocket lens.
HAIRS OF PLANTS.
The hairs of plants will furnish you with abundant ma- terial for study and delight throughout the summer long, and the variety in their form will astonish you. Look at the beautiful bead-like hairs of the Spiderwort — a rich purple chain of cells fringing each stamen. White, trans- parent, glittering rows of5 cells from the flocculent mass of hairs we see on the leaves and stem of the common Groundsel. The common garden Verbena has the mouth of its corolla closed by a dense row of beaded hairs pro- tecting its pistil. I cannot describe more, but look at these.
* These are called glandular hairs.
14 Objects for the Microscope.
Some are simple ; some are branched, or star-like, or tufted, and contain simply water : —
Alyssum leaf Draba verna leaf. Antirrhinum calyx. Tradescantia stamen. Verbena. Campanula. Nettle. Borage.
Chrysophyllum.
Verbascum.
Ivy.
Hibiscus.
Deutzia scabra.
Elseagnus.
Dolichos (cowage).
Groundsel.
Take the hair of a Borage stem or flower off at the base, and lay it on a slide with a drop of water covered with a bit of thin glass, and you will be delighted. The hair of the Nettle, with its poison gland at the base, must be ex- amined in the same way. The pain is caused by the breaking off of its point, and the acrid irritating liquid springing up into the wound.
The reason why these hairs are mentioned immediately after the cells and cell-contents is, because they are only prolonged and varied cells rising from the cuticle, and when the cell-walls thicken into fibre these hairs become thorns. Sometimes they expand and tbrm scales, as we see on the beautiful leaves of Hippophse and Elseagnus, which are mounted as detached scales for the polariscope, or in situ as opaque objects.
CUTICLE AND STOMATA.
The cuticle of plants is that transparent skin which we can easily peel off from various leaves, but especially from the Lily, the Candytuft, Iris, and the petals of flowers ; and prove by examination under a piece of thin glass and with a drop of water that it is really composed of a single layer of cells, having pores, called stomata, thickly scattered over it.
These slides are very useful to those persons who live "in cities, or who have not yet studied plant-life for them- selves ; and 1 doubt not that they will lead many a careless
Objects for the Microscope. 15
eye to look for other examples, and to find an endless variety in the garden and the field.
These pores, called stomata, are absolutely necessary to vegetable life. Leaves are the organs of respiration — the lungs of a tree, and the stomach also ; for they send back nutrition to the trunk and stem, take up the sap which rises from the root, give it the needful quantity of carbon, expose it to the action of the air, and cause the super- abundant moisture to evaporate. All this is done by the agency of the little dots we call stomata, And this is the way in which they act : — We see that the cuticle is formed of a single layer of cells ; these contain air and not fluid, as do the cells of the pulp or parenchyma ; also they are so closely fitted to each other as to confine that moisture which otherwise would be too quickly evaporated by a hot sun, and the leaf soon dried up and withered ; but at the same time, as air is necessary to the inner cells of a leaf or flower, these stomata, or openings, are placed in great numbers in the cuticle, acting like valves, which admit air freely, give out surplus fluid, and take in atmospheric moisture when required. They are bordered by cells of peculiar form, usually kidney-shaped, with an oval aperture in the centre ; and these " guard cells " dilate and con- tract, closing or opening the passage according to the ne- cessities of the plant. On a hot day they will close, to defend the inner cells from exhausting heat: in dry weather, when the stem does not give enough fluid for the nourishment of the leaves, then the stomata open at night and drink in the night-dew, but close again as soon as the cavities of the leaf are full. The number of pores in a square inch of surface is amazing; eg. we find that a square inch of the leaf of
Hydrangea contains . . 160,000 under surface
Iris „ . , 12,000 both surfaces
Houseleek ,, . . 10,710 upper surface
Tradescantia ,, . . 2,000 upper surface
Lilac ,, . . 160,000 under surface
Vine „ . . 13,000 under surface
16 Objects for the Microscope.
The stomata are generally largest upon succulent plants, and abound on the under side of all leaves except grasses and upright leaves, such as the Iris and Tradescantia, where they are found eqtiaHy on both sides.
CUTICLE OF YUCCA.
In the cuticle of Yucca the stomata are bounded by four cells, and are themselves somewhat quadrangular : there are about 40,000 of them in one square inch. The plant is a native of Peru ; called also common Adam's needle, bearing a handsome flower in panicles on a stem eight or ten feet high when in its native soil; but in British gardens it scarcely reaches three feet high.
CUTICLE OF ALOE.
The cells are somewhat different in shape, though the stomata are also bordered by four cells: they are more oblong, very prettily disposed, but require a power of 200 diameters to observe properly. First use the ^-inch, and then the £-inch.
CUTICLE OF DEUTZIA SCABBA.
This is a polariscope object.
The cuticle is siliceous (see Indian Corn), and the wavy outlines of the cells and the starry clusters of siliceous hairs are very beautiful. When gathered from the tree, these stars are white upon the green cuticle, and those of the upper surface are many-rayed, whereas those of the lower surface have usually but four or five rays.
This leads us to consider the use of those abundant hairs which clothe the living plant. They serve two purposes — for warmth to the tender bud, or for attracting moisture. On many plants they rise up towards evening and catch the falling dew ; then bending downwards at noontide they form a close layer over the cuticle, and give it a protecting shade, at the same time preventing a too rapid evaporation of the moisture they had attracted. There are many kinds of hairs on plants ; most beautiful are some of them, especially those which secrete oils or saccharine matter.
Objects for the Microscope. 17
These are called glandular hairs ; they rise up on a slender stem, and expand into a globular head, filled with coloured or white special secretions, such as we find on Sweet-briar and Moss-rose buds, or on the leaves and flowers of Collomia.
CUTICLE OF AMARYLLIS.
This example will show the two-lobed stomata, one kidney-shaped cell on each side ; it is from any part of leaf or stem of the common white Lily ; also compare the cells with those of the
CUTICLE OF INDIAN CORN.
This is what is called a siliceous cuticle. All the grass tribe and the plants called Equisetacese, or horse-tails, have the property of attracting silex or flint from the soil in which they grow : the cell walls and stomata become so impregnated with it, that even soaking in nitric acid, which destroys the vegetable part, leaves the skeleton, or frame- work, perfect, as in this slide, which has been thus pre- pared. Observe the finely-toothed edge of each cell, as well as the peculiar shape of the four cells bordering the pores. The stomata are very abundant in grasses ; they cover every part of the stem, and both sides of the leaves.
CUTICLE OF SACCALOBIUM.
The Saccalobium is one of the orchis tribe, a native of Asia, found in the Indian Archipelago, and is cultivated in hot-houses in England. The spiral fibre in some of its cells forms a regular network on the inner surface.
CUTICLE OF ELjEAGNUS.
This is an opaque object ; the scales are very beautiful, and when detached from the leaf and mounted in balsam they polarize.
The Elseagnus is a native of all parts of the world, from the northern hemisphere down to the equator, which it rarely passes. The flowers of this species are highly fragrant, and abound in honey.
18 Objects for the Microscope.
CUTICLE OF TILLANDSIA.
The under side of the leaves and the stem of this plant are adorned with delicate scales, as of the finest network.
The plant itself is a native of South America and the West Indies. The whole tribe dislike water; and Lin- naeus named the genus from a professor in Sweden, who, having once experienced a very rough passage from Stockholm to Abo, determined never again to cross the water ; he even changed his own name to that of " Til- lands," which means on or by land ; and actually, when obliged to return to Stockholm, preferred travelling 200 miles round by Lapland to going a direct road of eight miles by sea.
One species of Tillandsia (utriculata) which grows upon old and decaying trees in the forest of Jamaica, has leaves a yard long, inflated at the base, which form a reservoir for water. Each leaf holds about a quart of fluid, and wild cattle seek refreshment there. Travellers also, under the hottest sun, may turn aside and find a sweet pool of water in dry seasons, when all other supplies have failed.
CUTICLE OF ONOSMA.
The Onosma is a native of Tauria, near the Bosphorus. The plant is small, with handsome flowers, flourishing in sandy soil ; and this cuticle is very beautiful under polarized light,
CUTICLE OF OPUNTIA.
This beautiful cuticle is from the leaf of the Opuntia, a kind of Cactus or Indian fig, and on one of them the cochineal insect is found : this is from the Opuntia vulyaris, which bears a large purple juicy fruit, and is a spiny shrub, growing abundantly on Mount Etna amidst its lava. It is, however, a native of South America, and the way in which it has been naturalised and made most useful in Sicily is remarkable. As soon as a little fissure is per- ceived in the lava, a small branch or joint of Opuntia is stuck in ; the latter pushes out roots, which are nourished by the rain which collects round them, or by whatever dust
Objects for the Microscope. 1 9
or remains of organic matter may have made a little soil. These roots spread out and ramify into the most minute crevices, breaking up the lava into small fragments, and finally rendering it tit for culture.
L I T H 0 S P E R M D M.
from lithos, a stone, sperma, a seed.
The hardy stony seeds have given it this name, as well as the old English appellative Gromwell, from the Celtic grom, a seed, and mil, a stone.
The leaf of this common plant is extremely beautiful ; the hairs are not only bulbous as in borage, but cells are grouped around the base of each like a circlet of crystals. There are three species worth seeking :
The common white L. arvense, in cornfields.
L. officinalis, pale yellow.
L. purpurea, large blue flowers in chalky soil.
RAPHIDES.
These are crystals found in the 'cells of various plants. No better example can we have than the
CUTICLE OF HYACINTH,
m every cell of which we see a cylindrical crystal. Exa- mined with polarized light they are most distinctly seen, and enable us to understand the position of raphides in other plants. The Cactus, the common Dock, and various other vegetables, have bundles of needle-shaped crystals in their cells. Turkey Rhubarb and the garden Rhubarb have rectangular prisms of carbonate of lime grouped in a stellate form. See the slide of
RAPHIDES FROM RHUBARB.
What their use is we do not know. Another kind called cystolithes, are stalked and suspended in the cells of the nettle tribe. Their formation has been watched : first a little papilla or swelling is perceived at the upper part of a cell, which increases at the end into a clubbed form, from which crystals of oxalate of lime sprout forth.
20 Objects for the Microscope.
This is one of the mysteries of creation, how the cells of a plant so regularly secrete each its appointed store of need- ful substance for the plant-life — how from the earth in which it grows, from the air in which it lives, from the light which quickens it, each tiny chamber receives exactly that portion of nourishment, and that kind of nourishment which enables it to produce either the green wax which colours the leaf, or the white starch -grains, or the gum, the sugar, the oil, or the shining crystals, or that nucleus which is the reproductive cell — all this going on invisibly around us in every living plant, and having been thus going on for five thousand years at least, unseen, unknown by us, until the revelations of the microscope. Is there no deep thought stirred in our hearts by the manifest order and minute care of Him who built up this living temple for His own pleasure and for ours ? Do we think of all that is contained in the flower we gather by the way-side, in the herb that bends beneath our feet ? Is no desire kindled to see these things as they are, and pass on from these slides to the examination of the plant itself? There are a thousand things more beautiful than raphides that cannot thus be mounted or preserved. Shall I give one example only for a summer hour's delight ?
ANAGALLIS.
In the garden or the cornfield gather a little scarlet Pimpernel, the Anagallis, or the Poor Man's Weather- glass, that lowly and bright little flower which opens every morning at eight minutes past seven, and closes about three minutes past two in the afternoon. Examine it with a pocket-lens, and you will see that it belongs to the Primrose tribe, with its single-leaved calyx and corolla, wheel-shaped, deeply cleft into fine segments, fine slender filaments and heart-shaped anthers, one-thread-shaped and clubbed stigma. With the same lens you can examine the seed- vessel, a little globular capsule opening all round, and, raising the lid, observe the most beautiful dotted seeds lying closely pressed to the pitted receptacle ; and this, if once seen, will not be forgotten. Take it now to the mi-
Objects for the Microscope. 21
croscope, and, with a low power, first look at one of the coloured segments of the corolla. Press it lightly in a drop of water under a bit of glass, and you will then see that the edge of the petal is fringed with little bell-like glands, purple and white, and that hues of deeper colour radiate from the base of the petal. Put on a higher power, and you will find these are exquisite spiral vessels ; not one only, but many in each line, short, and joined to each other by a delicate dove-tailing process. Think of the mechanism in that one small leaf, and those little oil cells fringing it so prettily, doubtless for use as well as beauty. Then take off one stamen and look at it in the same way. Half way up the slender white stem are purple hairs, each jointed and like a row of tiny amethysts : above is the heart- shaped anther, with its golden store of pollen grains, out of each of which will flow the life-giving germ to the future seed. Take the style and stigma, and examine them next ; you will not soon be weary of the sight. Most likely you will find some pollen grains upon the stigma throwing down their tubes invisibly ; for this is only seen with a high power, and by making a very thin section of a short style, such as that of a Cistus, or a Chickweed.
After such an examination, that little flower will never be seen with the same careless eye which for years had passed it by unheeded, because unconscious of its beauty.
SPIRAL FIBRE.
Many specimens of these are sold prepared for the microscope, especially the following : —
Spiral cells of Oncidium. Spiral vessels of Collomia. Spiral fibre from Balsam.
Spiral cells of Sphagnum. Scalariform vessels.
They require some little explanation. We have already seen, in the examination of cuticles and flower-stems, that plants are made up of cells containing various substances, as starch, crystals, oil, or wax. These were for the nourish- ment of the plant ; but here are cells which are supposed
22 Objects for the Microscope.
to assist in the circulation of air and moisture throughout the system. Some of them strikingly resemble the trachea of insects, and seem to communicate with the stomata as the trachea do with the spiracles.
SPIRAL CELLS OF ONCIDIUM.
These beautiful little cells are obtained by macerating the pulp of those leaves which contain them, separating them with a fine sable brush, or mounted needle. The Oncidium is an orchis, a native of Peru, Mexico, and the West In- dian Islands ; cultivated in hot-houses in England. They are curious and beautiful plants, with spotted yellow or purple and white flowers, one species much resembling a gorgeous butterfly. In all these plants the spiral cells abound immediately under the cuticle, and, viewed with polarized light, they resemble coils of coloured wire.
SPIRAL VESSELS OF COLLOMIA.
These fibre-cells are in the cuticle of the seed, and the examination of them is so easily made, that it is well worth doing. The cells which contain the fibre are in this in- stance so delicate, that a drop of water causes them to break, and the coil unrolls, shooting forth in long tubes, with an appearance of life as they spring across the field of sight. To see this, take a seed of Collomia, and cutting off a very small piece of its skin, place it with a drop of water on a slide under the thin glass, when you will perceive the fibre uncoiling in all directions. The Collomia is a native of America, but naturalised in our gardens, where it grows like a weed, having pretty buff or pink-coloured flowers, covered with glandular hairs.
SPIRAL CELLS OF BALSAM.
These are from the common Balsam of our garden, and show the bundles of long cells made up of spiral fibre, which often break and pass into annular fibre : you may perceive some of these in detached rings. These cells con- tain air, and are those which most resemble the trachea of insects. Those of the Leek are also very remarkable, and
Objects for the Microscope. 23
the common garden Rhubarb will furnish you with abun- dant specimens. Take a little boiled Rhubarb, and pick it to pieces with a mounted needle in a little water, when bundles of spiral vessels will be easily found.
SPIRAL CELLS OF SPHAGNUM.
Sphagnum is a moss growing in marshy places, and its leaf shows a beautiful arrangement of spiral fibres in its large oval cells, whilst in the smaller ones you will see the granules of chlorophylle which colour the leaf.
SCALARIFORM VESSELS,
so called because they resemble the steps of a ladder, are peculiar to ferns and to asparagus. They are secondary deposits on the cell wall, and somewhat of the nature of spiral fibre. Under polarized light they are very beautiful. When you pull up a common Bracken or Fern, and cut the root across, the brown figure you see, called King Charles in the Oak, is made up of these scalariform vessels. They are very troublesome to prepare, but this is the easiest way that I know of:— Cut up the root and boil it until tender enough to peel ; put the centre part into a jam- pot with water and a little nitric acid ; let it stand in boiling water for some hours, then pick the long white fibres carefully out, wash them in boiling water over and over again until perfectly clean and clear, which is only ascertained by examination under the microscope, then mount them in fluid or balsam. If in balsam, dry them well first.
POLLEN.
POLLEN OF MALLOW.
A beautiful object viewed as an opaque — more lovely far when taken fresh from the flower, and looked at upon one
24 Objects for the Microscope.
of its own crimson leaves, or the petal of a Geranium. It cannot be worthily described : rest not until you have seen it ; and also the
POLLEN OF HOLLYHOCK,
which is like it, only the golden grains are larger, and per- haps more easily preserved. I usually take a portion of the stamen, studded with the spiked globular grains, and dry them on a scarlet petal of the flower ; but they are well seen on a black ground, simply mounted, when dry, between two pieces of glass.
POLLEN OF PASSION-FLOWER.
These are not spiked, but have three plain valves and a reticulated cuticle.
POLLEN OF CENOTHERA
is curiously triangular, with pores at each corner, from one or more of which the pollen tubes spring forth.
Pollen is always better observed fresh from the plant. The variety in shape and structure is very great ; the in- terest will be unfailing in the examination of it, the deeper we go into the mysteries of plant-life.
This golden dust, which, to the unassisted eye, is all alike in every flower, is fashioned with the most elaborate care for its great purpose, and sculptured with that exqui- site finish which all creation bears as the signature of the gracious God who made all things well.
This golden dust, contained by every flower in the few or many stamens which are the caskets of its wealth, is the fructifying principle which causes the seed to become fruitful, and without which no reproduction of a plant could continue, as it does, from age to age.
The purpose of this book being chiefly to explain the objects before us, I will not say more of the pollen-grain than that it must be examined both as a transparent object, with a drop of water or oil of lemon, and dry, as an opaque. Particularly observe the blue pollen of Epilobium ; the red
Objects for the Microscope. 25
pollen of Verbascum ; the black pollen of the Tulip ; the varied forms in the following flowers : —
Cucumber
Crocus
Cactus
Cruciferse (order)
Collomia
Campanula
Cobsea Scandens
Composite (order)
Geranium
Heath
Daisy (one of the Com
positae) London Pride Saxifrage Violet CEnothera Passion-flower Lupin Acacia
A FEW WORDS MORE ON THE POLLEN.
As I lay aside these slides, and desire you to seek for varieties of pollen in the fresh sweet flowers around, the thought arises tfiat some who read thus far may wish to know a little more of the structure of the flower they gather, and the pollen they examine ; else the microscope lesson loses half its value, and the student more than half his pleasure. If it is possible, read some better book — Lindley's works, or Balfour's * Botany/ where all is told, and illustrated by plates ; but if you cannot do this, then gather a flower and examine it thus : a Chickweed will be easily obtained, and is the best for a microscope lesson.
The organs of generation in flowers are the stamens and the pistil : the stamens varying in number from two to upwards of twenty ; and the pistil, which occupies the centre of the flower, having from one to many styles, the upper part of which is called the stigma. The base of the pistil, which is swollen and round, is the ovary. Cut it open with a penknife or lancet, and you will see tiny white cells on either side, which are the rudiments or beginning of the future seed. The pollen fructifies each seed whilst growing in the ovary, and the Avay in which it is accom- plished has only of late years been discovered.
The stamens are filaments bearing at the top single or double caskets, called anthers, full of pollen-grains. When
«
26 Objects for the Microscope.
a flower first opens the anthers are closed all round ; but as soon as the air and the light have perfected the pistil and caused it to secrete a kind of gum, or viscid liquid, on the surface of its stigma, intended to hold fast the pollen-grain, the anthers open and the golden dust appears, falling on the ready channel, which conveys it to the ovary beneath. The pollen-grain itself is not a simple cell, as we might at first suppose : minute as it is there are many cells therein, and a subtle fluid, called fovilla, which is in reality the life- giving principle to the ovule. When a pollen -grain falls upon the stigma it presently opens one of its pores, and sends forth a tube more or less long, which descends through the tissues of the style, enters the ovary, reaches a tiny ovule, and pours it into the fovilla, which fovilla forms the embryo or future plant that is preserved and nourished in the seed.
Take a little pollen from a Cucumber plant or Passion- flower, and when it is fairly under the microscope, covered with thin glass, let a drop of water run in. The moisture is absorbed by the pollen-grain, and it throws out a tube and discharges the fovilla. It goes off like a little cannon, a cloud of fovilla waving on the slide.
The quantity of pollen in a flower is astonishing. A flower of the Peony, for instance, has about 174 stamina, each containing 21,000 granules, — total, 3,654,000 pollen--
f rains. A single Dandelion has 243,000 pollen-grains, 'he contents of one anther are quite sufficient for the fruc- tification of all the ovules ; but the superabundance is not wasted, for thousands of insects live on the golden store, and the busy bee fills her baskets hourly with these pretty cakes lor her nurslings.
POLLEN-TUBES.
To see the actual pollen-tubes in their passage down the style is a more difficult matter ; nevertheless, with care and a good glass it may be managed. Put on the J-inch and choose a flower with a very stout style, — a Cistus or this Chickweed; the flower must have just faded, then you may be sure the ovules are fructified. With a sharp razor make
Objects for the Microscope. 27
a very thin section of the pistil, and lift it with a fine sable brush on to a slide in a drop of water, and cover as usual with thin glass ; focus carefully, have good light, and you will see the pollen-tubes actually descending the tissue of the style.
Now we are considering a great mystery. We see how varied are the lengths of styles and pistils, yet shorter or longer the pollen-tube stops not until it reaches the ovary, and when there, amidst the many rows of ovules, in many positions, it has to seek the one spot in each ovule by which alone it can enter, and there, and there only, it rests. Perhaps all but one have been fertilised, and are closed — ft seeks that one and perfects the work. Thus we see the all-directing, all-sustaining, life-giving power of the Omni- present one ; we see His presence in the tiniest flower. He alone knoweth how this may be, — we only see that it is so ; and reverently let us ever search into the mysteries of crea- tion, and find new and deep delight in these revelations of His secret order, wisdom, and care for the preservation even of the flower of the field.
STAMENS.
The shapes of stamens are also to be noticed. Some open lengthwise, some across ; some have valves like fold- ing doors, flying upward, as in the laurel tribe. The anthers of the barberry are on jointed filaments, which are exceedingly irritable, and, if touched by the smallest insect, spring up and scatter the pollen on the pistil.
Euphorbia, or spurge, — a common weed in every garden, —has a pistil which hangs outward and downward, appa- rently out of reach of the pollen. The anthers rise up and shoot it out like little guns, one after the other, at the stigma of the flower.
Nettles also have beautiful elastic filaments for scattering the pollen on the pistil, which is in a separate flower. Many plants have these organs thus separated, but pro- vision is ever made for their union, as in the case of our cucumbers, where bees and flies carry the pollen from one flower to the other.
28 Objects for the Microscope.
SEEDS.
Having said a little on the beginning of the seed in the ovary, we shall be prepared to look at the seeds themselves with greater interest. Here also we have an endless variety of beautiful microscopic objects : —
POPPY SEEDS.
viewed as opaque objects, show a reticulated surface ;
SWEET-WILLIAM SEEDS,
oblong and dotted ;
SILENE, OR STELLARIA,
beautifully fretted and sculptured —
Foxglove
St. John's Wort
Saxifrage
Geranium
Anagallis
Portulaca
Passion-flower
Begonia
Scropularia
Hyoscyamus.
Look at all these ; and, above all, get a prepared slide of the exquisite
ORCHIS SEEDS.
The'y are like little net-purses, with the seed in them : the loose net is the skin or cuticle of the seed.
ECCREMOCARPUS OR CALAMPELIS SEED.
This winged seed is a splendid object for the polariscope. The Eccremocarpus, a beautiful creeper, with large bright- coloured, trumpet-shaped flowers, is a native of the tropics.
SEED OF CENTAUREA CYAN US.
The section of the seed of this plant is an excellent object for the binocular. It is common in corn-fields, with small purple florets of the disk, and large bright-blue florets of the ray. Named from the centaur Chiron, who was said to have cured himself of a wound in the foot with the leaves of this plant.
Objects for the Microscope. 29.
CHAPTER II.
SECTIONS OF WOOD.
THE use of these sections is to show the structure of the stem of plants, and the difference between the two great divisions of the vegetable world into endogens and exogens. An endogen is a plant which has long straight-veined leaves like a Palm, a Cane, a Lily, Iris, Daffodil, and all the grasses. The flowers are usually divided into three, or a multiple of three ; the embryo has only one seed-lobe, or cotyledon, and the stem is like the section of
RUSCUS,
or Butcher 's-broom, a common shrub in waste and watery places, with very rigid dark-green leaves, dipped by a sharp spine : it blossoms in April, but is chiefly admired for its large scarlet autumn berries, one in the axil of each leaf. This pretty section — apparently a fine lace-pattern — shows the structure of an endogenous tree ; it grows from within, and is composed of a dense mass of simple cells, in the midst of which, in varied patterns, run upwards bundles of denser cells called " fibro- vascular" ; and each bundle has one or more ducts, best seen perhaps in a section of
WANGHAE CANE.
Sometimes the centre cells disappear and leave the stem hollow, as in the grasses* and many of the water plants. Compare now this slide, and also a section of
ASPARAGUS,
with that of the Hazel or Apple.
SECTION OF HAZEL.
Here we see very distinct organization on quite a different plan. The exogen has veined and reticulated leaves ; the
30 Objects for the Microscope.
seeds have two lobes, or cotyledons ; the flowers are arranged in four or five. The wood grows by the addition of cells, in circles, to the exterior of that last formed, and we see distinctly the open cells of the pith in the centre ; the medullary rays running from the centre to the bark at intervals, with sap-vessels and cellular tissue in circles, as they were added on.
CEDAR OF LEBANON,
a firm, dense wood ; the cells are very minute, the circles very distinct ; each circle is a year's growth, and the medul- lary rays are very fine and numerous, radiating from the centre. Those dark bands forming the circles are made up of vascular tissue, or woody fibre, composed of long pointed cells, which overlap one another, and deposit internally a strengthening wall of a substance called scleragen, which is most abundant where not only density but great power of resistance is required. When young these woody fibres conduct the sap with facility through both stem and branches, especially of the fir tribe ; but after they are thickened they only afford support, and become what car- penters call " heart-wood." The sap-vessels of trees are those nearest to the bark, which makes the barking of trees so dangerous to their life.
SECTION OF PINE.
Look next at this section, because it shows some pecu- liar dots on that same woody fibre, called glandular dots, and which are remarkable as belonging to that tribe, and also at one of the yew tree (Taxus).
SECTION OF YEW.
Iii this section, if vertical, there is a beautiful com- bination of spinal fibre with coniferous pits.
These pitted structures require explanation, especially as those of the pine or common deal are used as tests of the defining power of the object-glass. The pits in coniferous wood are surrounded by a broad rim.
The origin of the pitted cell is in the unequal deposit of
Objects for the Microscope. 31
secondary matter inside the cell- wall. Always remembering that a young cell is a simple sac of a single membrane, which, containing a certain fluid, is capable of secreting vnrious substances, curiously separated from, or combined with, the various gases and inorganic matter which form the soil in which it grows. These secretions are used for strengthening the cell-walls, as the young plant springs upward ; therefore, if the deposit inside the cell is uneven, it causes marks on the cell-wall ; if the cell grows faster than the supply of deposit, the markings are spiral or arched, or waved, or dotted ; and these are best observed by comparing different cells from fresh plants. The anther of the vegetable marrow, if peeled and then examined with a drop of water, will give beautiful cells of arched fibre. But, to continue with this slide, — these pits are at first only dots in the secondary deposit ; then as the cell thickens these pits deepen, the primary membrane breaks, and they become channels from cell to cell, as you may see in a sec- tion of vegetable ivory, where you perceive radiations from each cell, which are, in fact, these deep pits, and in a vertical section would look like the pitted cells of Fir, or Clematis, or Lime-wood, or Laurus sassafras, and many others.
VEGETABLE IVORY.
Vegetable ivory is the seed of a palm called Phytelephas macrocarpa, and is composed of a large round mass of bony albumen, in which a small embryo is imbedded. Slices of this ivory-like albumen, placed under the microscope, afford very beautiful examples of these thickened cells.
FOSSIL CONIFEROUS WOOD.
Fossil coniferous wood, which is wood converted into lignite, or a kind of coal, when the vegetable matter is almost entirely removed and replaced by silex (flint), pre- serving all the peculiarities of structure. This fossil wood, from Tasmania, will show the pitted ducts, which prove it to be one of the Coniferse, or family of firs.
32 Objects for the Microscope.
Always add to your collection sections of
FOSSIL PINE WOOD,
vertical, horizontal, and tangential.
SECTION OF COCOA NUT.
This gives an example of cells thickened into very con- solidated woody tissue.
SECTION OF COB NUT.
The cob nut, or hog nut, is the seed of a plant (Omphalea), belonging to the natural order of Euphorbiacea?, native of Jamaica.
SECTION OF SNAKE WOOD.
This is the wood of a plant called Ophioxylon,* from its twisted root and stem, resembling a serpent. It is found in the East Indies, sometimes as a climbing plant, bearing bright red and white flowers ; sometimes as a small shrub, the root of which is a famous nostrum with the native physicians.
MOSS. SLIDES OF DICEANUM, FUNARIA, ETC. ETC.
There is no season without its beautiful symbols of God's power and love, His wisdom and forethought. Spring flowers fade away ; the summer foliage withers and falls from the trees ; the autumn soon loses its crown and the last of its flowers ; but hardly have the lingering Dandelion and little Daisy left us than on every old wall and knotted trunk we find, in rich profusion and variety, the capsules or seed-vessels of the pretty mosses.
They are our little way-side friends, — we often gather their trailing stems and leafy sprigs ; but few persons, com- paratively speaking, pause to examine their exquisite seed- vessels ; therefore a few mounted specimens will be of great value in the collection for our microscope.
* Opliioxylon, from. #$is, a serpent, and |t>Aor, wood ; because it has a twisted root and stem.
of Insects.
1 Plate 4.
^••N»^_ -^ *v ^ ^ ' ^v >*v ^t ^
1. Wing of Earwig, shewing its method of folding up.
2. Wing of Earwig, magnified 4 diameters. 3. Earwig flying, natural size.
4. Wing of Whirligig- beetle, magnified 5 diameters. 5. The same natural size.
6. Minute portion of Beetle's wing, magnified 420 diameters. 7. Wasp's wing, folded.
8. Wasp's wings, hooked together, magnified 3 diameters.
9. Hooks on Wasp's wing, magnified 60 diameters.
Objects for the Microscope. 33
Before I describe the growth of a moss or the slides before us, it is necessary to learn the several parts of its fructification, arid, if possible, to procure specimens of each of them.
A moss is a flowerless plant ; the fruit or seed-vessel is the only visible organ of reproduction, and consists of —
The capsule, or urn-like body, which contains the spores.
The operculum, or lid of the capsule, which shuts in the spores until they require light and air.
The calyptra, or veil, which protects the young capsule.
The peristome of the capsule, which in most of the mosses is set round with a single or double row of teeth, such as you see in Dicranum or Bryum, and which are curiously regular in their number, varying from four to sixty-four, but always a multiple of four. Remark this in any you may examine ; there will be four or eight, sixteen or thirty- two, and one variety (Polytrichum) has sixty-four; but there will be no odd number.
The inner peristome, or cilia, a fringe of delicate inner teeth, often rising like a cone in the centre of the capsule, pale yellow, or pure white, whereas the outer row is usually crimson or brown.
The columella is a column in the middle of the capsule, round which the spores cluster, and which you will only see by carefully dividing an unripe capsule lengthwise, making a thin section, and looking at it with a drop of water under a low power, when it will delight you.
The growth of a little moss is so interesting that we shall do well to watch it in our winter walks, from November to April.
Botanists are not yet quite agreed about the green filaments, which are the first appearance of fructification, and whose different cells contain the germs of the future moss. They are called antheridia and pistillidia, analogous to the stamens and pistils of a flower, but very different in their structure and action. Read the chapter on the structure and reproduction of moss in ' Carpenter on the Microscope ' ; or, better still, read Hooker and Taylor's ' Muscologia Britannica.'
34 Objects for the Microscope.
The part that \ve can daily observe with a simple pocket lens is this : — The little capsule rises from its mossy stem wrapped in a delicate leaf, which breaks from its stalk, and is carried upwards in the growth of the tender bud it is to protect from the winter cold. This leaf forms the calyptra before described, and varies in colour, form, and substance : on some species of moss it is quite transparent, of bright green or pale yellow ; on some it is hairy and thick. By-and-by the calyptra falls off, — splits up the side, or comes off whole,— and then the capsule is seen, wholly formed, but closed by its lid or operciilum. This also varies much in form and colour ; sometimes, as in the tiny Weissia on stone walls, it is bright apple-green, tipped with scarlet or crimson, very beautiful to look upon even thus ; but none could guess at the exceeding loveliness concealed beneath this pretty lid, nor without a microscope could we see further into its mysteries.
If we take an unripe moss and divide it, we perceive the spores clustering round the columella, and growing in warmth and security within the closed capsule. But an appointed time comes, and then the operculum opens, falls back, and we see the peristome surrounded with a double or single row of teeth, — four, sixteen, thirty-two, or sixty- four, always an even number and multiple of four, as I have before observed, — the outer row rich crimson or brown, and the inner cilia pure white or pale yellow, forming an exquisite network as they bend protectingly over the mouth of the capsule, allowing the imprisoned spores both light and air, yet saving them from cold and wet and tiny insects, until they are perfected and ripe for dispersion. When their work is accomplished the cilia open, the little teeth unclose, and the spores fall to the ground, or are borne upon the winds hither and thither, to vegetate wheresoever it pleaseth God that they shall grow. All this care hath He taken of the spores of a tiny moss ! Yes ; and these mosses occupy no unimportant position in the economy of nature. They are, with lichens and fungi, called servi, or servants, because they are the earliest forms of vegetable life, and prepare the soil for higher
Objects Jor the Microscope. 35
plants. In the most desolate regions, in the coldest •climate, the little moss is found. This very Dicranum, at least its species Dicranum bryoides, was once the friend of the great traveller, Mungo Park. He was bewildered in ii desert, and, over-weary even unto death, had laid himself down despairingly to die. As he did so, a little Dicranum caught his eye ; the sight of its beauty touched him, the thought of God's care for it awakened the better thought of — " If God so cares for the grass of the field, which to-day is and to-morrow is not, does He not much more care for me f " He rose up, tried once more to find his way, and was saved.
Mosses abound everywhere; they fill even the rank bogs, and form rich mould for the aristocrats of creation ; they cluster round the wild flowers, and protect them in their •earliest state from cold and injury. Servants of creation, servants of God, they fill their appointed place, and do their Maker's will, beautiful in their lowliness as the state- liest oak of the forest.
THE DICRANUM
is found from November to April, in hedges or clay banks.
FUNARIA HYGROMETRICA
is to be viewed as an opaque object. The crimson peri- storne of twisted teeth and the white cilia gathered into a silvery knob in the centre is one of the loveliest objects we can look at. They are best gathered fresh, and all the winter long we find them on walls and in hedges, or waste places, especially wherever wood has been burnt, or near railway stations.
The leaves of mosses are made up of cellular tissue, and in a young leaf of Eunaria we see the chlorophyll-grains very distinctly. They want no preparation beyond placing under thin glass with a drop of water.
The capsules of Dicranum and Weissia are better mounted in balsam ; and Eunaria is best seen when simply gummed on a circle of black paper, and protected by a cell of cardboard and thin glass.
36 Objects for the Microscope.
There are upwards of forty genera and a thousand species of moss, of which 39 genera and 400 species are found in Great Britain.
SPOKE-CASES OP FERN.
The fructification of ferns affords a great variety of microscopic objects, though we rarely find any but the spore-cases of the common Polypodium mounted in this way ; therefore, after looking at the slide, we should by all means collect and examine as many varieties of fern as we can, not only for the shape of the thecse, as these little cases are called, but for their position on the frond.
This Polypodium is a most common fern, growing upon old walls and hedgerows, and the round yellow spots on the underside of the frond are masses of these spore-cases called sori.
Observe that each theca is clasped by an elastic ring or band, called the annultis, and the spores are kept safely during their growth, as in a golden casket ; but, as soon as they are fit for dispersion, the membrane which encloses them breaks, and the elastic band is seen with an empty little cup at each end. The spores themselves resemble pollen-grains, and are very prettily marked ; but will require a higher power, and had better be examined from a fresh frond, with a drop of water, or a drop of oil of lemon, which is an excellent assistant in the observation of pollen and spores of all kinds.
The great profusion of these organs of reproduction is astonishing. If we take a leaf or frond of the common Hart's-tongue (Scolopendrium), and count those brown lines on the underside, which are the sori, we find at least fifty in a good-sized frond ; in each sorus 4,000 of these tiny thecse, sometimes 6,000; and the theca3 themselves enclose about fifty spores : thus we shall find that a single leaf of the plant may give rise to no fewer than ten millions of young ferns.
An interesting experiment may be made to learn the growth of a fern, by simply shaking some ripe spores on a saucerful of fine mould, covering it with a bell-glass or
Specimens of Hnir, magnified '200 diameters.
Flute 7.
2. Hair of Horse.
Objects for the Microscope. 37
tumbler, and keeping it moist, warm, and shaded. In a short time a thin green film will spread over the soil, which take up carefully on the point of a lancet, and examine under the microscope. The little spore first becomes swollen, angular, and bursts, throwing out a fine rootlet, which fixes in the soil and draws in nourishment. Then a number of delicate transparent cells are formed from the mother-cell in the spore, making a little green scale, which as it expands throws out many fibres or rootlets on the underside. The wonderful part is that this tiny green scale produces two kinds of cells, which fructify each other, as do the stamens and pistil of flowering plants.
One set of cells, called antheridia, contain most curious spiral filaments, which move spontaneously, and wheel round and round until the cell breaks, and they escape to enter into the other kind of cells, called archegonia, or germ-cells, from which the real stem of the future fern is produced. This is difficult to watch, and it requires a power of 300 diameters to see these moving filaments, called antherozoides ; but the development of the little fern is m itself worth seeing and mounting for the microscope in its several stages.
Ferns are amongst the flowerless plants, — very numerous, very useful ; not fewer than 2,000 species inhabit various parts of the world, from the tall Tree-fern of the tropics, more than fifty feet high, to the humble Spleenwort (Asplenium ruta-muraria) which haunts our ruined walls. Their claim to usefulness rests on their medicinal pro- perties ; the thick mucilage from Adiantum capillus Veneris being a famous cough nostrum ; a decoction of Polypo- dium is taken as an anti-rheumatic and sudorific beverage ; Osmunda reyalis is given to rickety children as a tonic ; and others are used as styptics and purgatives. The roots, when roasted and peeled, are eaten by the natives of New Zealand as we eat bread.
Shirley Hibberd's < The Fern Garden ' is a most useful companion in a country walk, to assist us in recognising the different species.
38 Objects for the Microscope.
ELATERS OF EQUISETUM.
This slide is useful chiefly in directing attention to the plant from which the elaters are taken, and as leading the student to an interesting experiment.
The Equisetacese, or Horsetails, are leafless plants found on moist ground, in ditches and rivers, with whorls of long slender branches, and a hollow stem which gives the micro- scopist a very beautiful siliceous cuticle with stomata. The fructification is found in the spring : a fertile scaly head rises from the earth, having circles round it of shield-like discs, beneath which the spore-cases and these spores, which then appear only as a fine green dust, lie concealed.
Shake a little of the dust on a slide of glass, and innu- merable small bodies will be seen, each with four elastic filaments clasping and unclasping them in quick motion for several minutes. If dry and motionless, by lightly breathing on them the action will be repeated. These are the elaters of the Equisetum, and the mechanism by which the spores are dispersed.
ELATERS OF JUNGERMANNIA.
Jungermannia, or Scale-moss, is a plant of lower rank in the vegetable world than the true moss, such as Dicranum or Funaria. The elaters which are here mounted belong to that species called Jungermannia dilatata, which creeps over the bark of trees, and tints the trunk of an old elm or oak with a rich brown or crimson ; here and there a patch of this scaly plant encrusting the rugged surface, and requiring the aid of a pocket lens to see its fructification.
Any time from November .to March look closely at one of these dark masses, and you will see dotted over it tiny globes, white as of frosted silver, rising on a slender stem, and perhaps great numbers of exceedingly minute fawn- coloured flowers. If you gather one and examine it with a good glass, small tufts of spiral fibre will be seen on each segment of what seems to be a flower — these are the elaters. Now this is not a flower, but a simple spore-case. The little white globe before noticed splits into four valves, and these elaters of spiral fibre uncoil with a spring and scatter
Objects for the Microscope. 39
the ripe spores. There are seventy species of British Jungermannia, which have been admirably described and delineated by Sir William Hooker. We can find several of them in our country walks anywhere, and the leaves of cellular tissue are particularly worthy of observation under the microscope.
JUNGERMANNIA BIDENTATA.
This is an example of the delicate toothed leaves of one species. We find another, Jungermannia furcata, very commonly on the same tree as J. dilatata ; it has a narrow green frond, forked at the extremity, and on the underside we may see the anthers, or anthendia, the male organs of the plant. They are small green globules, which cannot be properly observed without a microscope.
The elaters are best seen when mounted in balsam ; the leaves either dry or in glycerine.
FUNGI. SLIDE OF PUCCINIA, OR PHRAGMIDIUM.
Before we appreciate this apparently simple object, it is needful to learn something of the vast extent and variety of the family to which it belongs ; but the limits of this catalogue will not allow of more than a very brief state- ment of necessary information.
The Fungi are plants of low organization, of which the highest in rank is the common Mushroom, the lowest that fine mould or tiny spot which we find on dead leaves or decaying wood, or as a film upon our preserves, or a tiny forest on our stale paste. Everywhere, in short, we may gather specimens of Fungi, and find beautiful life in death under the revealing power of our microscope.
Few of them are at present mounted for the student, but this species may always be obtained ; it is a fungus parasitic on the Rose-tree.
The Puccinia is a mildew which infests the straw of Wheat, the leaves of Roses, Blackberry, Potentilla, Box, and Ground-ivy. We merely see small black spots, usually
40 Objects for the Microscope.
surrounded by a circle of orange- coloured cells, which if we scrape off and soak for a minute either in turpentine or diluted nitric acid, each particle of black dust (for it appears nothing more to the naked eye) is found to be a pear- shaped seed-vessel, divided into compartments containing spores. This Puccinia of the Rose or Blackberry has from five to seven compartments, or spore-chambers, and is the best specimen to collect for observation. Some botanists call it Phragmidium, and Aregma.
If you wish to see the actual escape of the spore, scrape the fungus from the leaf, and let it soak in a little alcohol on the slide to disperse the air. Before the spirit has quite evaporated, add a drop of nitric acid under the thin glass cover, and warm it over a spirit-lamp, press the glass gently, and in all probability the inner cell of the spore-case will come out, enclosing the spore itself.
To see the germination of Puccinia, you have only to scatter some of these spore-cases in the spring on some moist flannel, or on a floating piece of cork, when they will presently throw out long colourless filaments, at the end of which three or four septa will be seen filled with orange- coloured endochrome or pulp of granular matter ; then a spicule will rise on each septum, and expand into a globular head, into which the orange-coloured matter will pass, and these eventually fall off and begin to germinate on their own account.
The spores of fungi, being light and excessively minute, float in the air, enter plants through the stomata, and ger- minate in the cell beneath.
BLIGHT OP WHEAT (SMUT).
This is a fungus of globular form, black and powdery, covering the young ears of corn like a coating of soot. It is called Uredo segetum. The spores are so exceedingly minute, that upwards of seven millions eight hundred and forty thousand of them would be required to cover a square inch of surface.
UREDO FCETIDA OR BUNT,
is another species, also blighting the wheat, but found in the grain, which looks dark, though otherwise like the sound
ill's of Moths and Butterflies.
Plate 6.
10
1. Wing of Herald Moth. 2. Spot on Herald Moth's wing, magnified 60 diameters. 3. Eye-like spot on wing of Emperor Moth. 4. Part of Eye-like spot, magd. «0 diams.
p. Scales of Underwing Moth, magnified 80 diameters.
7 . Brimstone Butterfly. 8. Scales of Brimstone Butterfly, magnified 150 diameters. 9. Scales of Red Admiral Butterfly, magnified 100 diameters. 10. Scale, magd. 150 diams.
Objects for the Microscope. 41
wheat, until it is crushed, when a fetid black powder is seen, the spores of which are larger than those of the smut. Nevertheless, each grain contains four millions of them. They are of an oily nature, so that they stick to the healthy grains, and, if sown with them, infect the next crop ; therefore farmers dress their wheat with potash to destroy this fungus.
UREDO, OR jECIDIUM.
I mention this, although few specimens are mounted, because it is met with abundantly throughout the autumn and winter on the underside of the Coltsfoot leaf, on Spurge in our gardens, on the twigs of Fir-trees, and on almost every garden vegetable. These yellow spots on leaf or stem are beautiful microscopic objects. The orange-coloured spores form under the cuticle, which breaks sometimes like a cup, or coronet, full of golden dust, that is most interest- ing to the observer.
I will only add that there are 4,000 species of fungi, most of which are parasitic on plants and animals. The human body is also subject to their growth — the internal parts, as well as the bulb of the hair, the tongue and palate. The tartar of our teeth is partly a fungus, and so is the thrush in infants.
We can find a rich store of curious and beautiful forms on every dying leaf or decaying stem. Examine the mould on paste or jam ; the Puccinia on Rose-trees, Beans, Black- berries ; the ^cidium, growing in bright-red spots, on Gooseberry and Barberry leaves in June and July ; also on the white film on leaves of the garden pea. ^Ecidium is called erysipJie, and has little spore-cases dotted over it. So also on the leaves of the willow, a lovely little erysiphej each black dot fringed with hooked filaments. These will give some idea of the variety of fungi, and their invisible and unknown beauty. Look over Greville's work on the Cryptogamia, and Mrs. Hussey on the Fungi ; or get at Bulliard's fine old book on Microscopic Fungi, when your winter walks will abound with hitherto undreamt-of objects of delight:
3
42 Objects for the Microscope.
CHAPTER III..
INFUSORIAL EARTHS.
THESE slides, which require high power and a good microscope to examine, consist of specimens of Diatomacese from different part's of the world. Their value is in pro- portion to the knowledge of their possessor concerning the DiatomaceaB generally and particularly. The Diatom aceae are minute vegetable forms, called also " brittleworts," from the almost unavoidable separation of their cells or frustules in handling them. Long have they caused dis- putes as to their animal or vegetable nature. Very eminent naturalists, such as Ehrenberg, seeing them gifted with spontaneous motion, — the little golden Naviculse sailing slowly across the field of vision, apparently turning back when meeting with an obstacle, or whirling gently round as if by their own will, — decided that they were surely animal, and classed them with the Infusoria, which are microscopic animals, found in salt and fresh water. But later researches and patient investigation have placed beyond doubt the vegetable nature of these beautiful crea- tions, to whose variety there appears no limit.
As the wondering astronomer discovers the infinite worlds revealed in unfathomed space, and sees star after star arise in countless myriads within the dim and distant nebulaB, — as his mind bows down overwhelmed by the sense of the omnipotent Creator's dominion and guidance of all those glorious orbs, — even so the microscopist bends in astonished awe before the infinitude of God's works in the uncountable varieties and exquisite beauty of the minute Diatoms.
BILIN SLATE. — Wherefore are they thus highly wrought, and why in such abundance ? Take up that slide of Bilin slate, and know that in one single cubic inch 40,000 millions of these delicate forms are found !
Objects for the Microscope. 43
RICHMOND. — Look at the earth from Richmond — it is a very small quantity of a marine deposit — eighteen feet deep, underlying the whole city of Richmond, U.S., and extending over an area whose limits are not known.
ALGIERS, ORAN. — Observe the beautiful discs in that slide of earth from Algiers. Use the highest power that the art of man has yet constructed, and hardly will you see all the beauty which the finger of our God has traced on the circular valves of these little Diatoms, called Coscinodiscus, Actinocyclus, Arachnoidiscus, or Heliopelta. These names sound hard and perplexing to beginners, but they are full of meaning to any one acquainted with Greek ; and there is this great advantage in such nomenclature — that it is un- derstood alike by scholars of all nations. The difficulty of scientific names lies not in the names themselves, so much as in our deficient education, which wastes the time and the intellect of young ladies in acquiring accomplishments and modern languages without the solid foundation of Latin and Greek, which is acknowledged to be essential for men. These discs, and some others most commonly mounted as objects for the microscope, will be explained presently ; it is necessary previously to say somewhat more of the Diatomacese generally.
And, first: They are now decidedly placed in the vege- table kingdom. They are found to consist of simple cells, whose membrane is so thoroughly impregnated with silex (flint) that it is indestructible by those powerful acids or by such heat as would totally destroy a simple cell-membrane. They consist always of two valves united at the edges, like a bivalve shell, and containing endochrome, like the plant- cell ; sometimes oil-globules, and a granular substance which has been seen to circulate within. For a proper understanding of this read ' Carpenter on the Microscope ' ; ' Smith on British Diatomacese ' ; ' Pritchard's Infusoria ' ; ' Annals of Natural History,' 1843 and 1848 ; ' Microscopic Journal/ 1854.
The markings upon the valves, and their shape and position, are the distinguishing characters which decide the species.
44
Objects for the Microscope.
They are found in the living state abundantly in every pond and ditch, ocean and rock-pool. They are in immense deposits in every part of the world. A mud-bank, 400 miles long and 120 broad, has been found on the flanks of Victoria Land, wholly composed of these siliceous valves, or loricse. In Sweden and Norway they are used under the name of bergh-mehl, and mixed with the flour for bread. In the masses of guano these imperishable Diatoms are found in profusion, having been eaten by shell-fish, re-swallowed by the sea-bird, and passed through its digestive organs, to reappear unharmed, in all their beauty, as you may see them on the slides sold as " discs from guano."
DIATOMS OF GUANO.
It is not possible to catalogue the contents of the slides sold as infusorial earths from various parts, because every slide has a different collection, and the student should care- fully study each slide, and learn its contents, with the help of such a book as f Pritchard's Infusoria.'
The earths from the following places contain some of the most beautiful forms :—
Algiers
Mull
Bilin
Italy
Barbadoes
Auvergne
Richmond (discs)
Bangor, U.S.
New Durham
Kieselguhr
Lapland
Gossa
Obero
Habitchtswald
Tullamore
Lock Mourn e
Premnay
Wreatham, U.S.
NAVICDL^!.
Virginia (discs)
Piscataway
Manchester, U.S.
Rappanhanna
Schockhoe
Rugen
Slieve Mor Hills
Bermuda (discs)
Some Diatomacese, however, are mounted separately, either as test-objects, for their delicate striae, or for their peculiar markings ; and none more frequently so than the Naviculse, of which Navicula hippocampa, or Pleurosigma angulatum, are favourite examples.
Objects for the Microscope. 45
NAVICULA HIPPOCAMPA.
The Navicula? comprise the largest section of the whole body of diatoms, and vary very much in form and markings, but the genus Navicula? itself is so called from its resem- blance to a boat or little ship (Nave, a ship). They are found, both in the living and fossil state, of a bright golden colour, the valves delicately striated, with or without a central aperture. Some are striped longitudinally ; some transversely ; some waved or shaped like the letter S, as
PLEUROSIGMA
in which the apparent stria? are resolvable into hexagonal dots under a high power. These Navicula? all multiply by division and conjugation, as do the diatoms generally, which cannot be explained without plates, and the student must refer to the works already mentioned.
MELOSEIRA, From melos (a member), and seira (a chain),
is found on marine algse, a composite plant of man^ frustules, joined together by siliceous hoops.
MELOSEIRA BORRERI.
No student should be without a slide of Meloseira, because it is a diatom very likely to be mistaken under a low power for a mass of conferva?. In fact, it has been misunderstood even by eminent naturalists. Agardh, the Swedish botanist, found and classed it with the fresh-water alga? ; Ehrenberg examined and removed it into the animal kingdom under the name of Gallionella; and now it is replaced in the vegetable world as a diatom, its siliceous lorica being quite ascertained, and many beautiful species found both in salt and fresh water. If possible, obtain a specimen of Meloseira sub-flexilis, which is found off ifriburg ; or Meloseira nummulites, found in the Baltic Sea ; but meanwhile observe this M. Borreri, which is abundant on marine alga?. You see a mass of bead-like filaments, which towards the edge is better seen and with a high
46 Objects for the Microscope.
power. The frustules, or valves, are quite apparent— cylin- drical, round at the edges, and with a strongly-marked central line. Some of the frustules are larger than others ; in these most likely the process of self-conjugation has begun.
ACHNANTHES LONGIPES, From achne (chaff or down), and anthos (a flower).
These now scattered frustules were connected in life by a stem, and the upper and lower frustules had different markings. You may observe that some have a transverse line, forming a cross upon the valve ; this is one of the lower frustules. Achnanthes are common in sea-water, attached to algae. There are several species, — some fossil, others found in fresh water ; but this is the most beautiful.
SYNEDRA ULNA,
From sunedra, (a sitting together),
are common in fresh water, sitting together in groups of golden, wands, striated and open at the ends, which in age dilate, and three obtuse teeth are visible, with openings between them. These often occur in such numbers as quite to encrust the confervse, or the stones in ponds and rivers.
We need but to take a very little of the brown-looking vegetation which we find on the walls of wells or horse- troughs, or quiet ponds, and placing it on a slip of glass, with a drop of water, cover with another piece of thin glass, to see many of these living microscopic plants.
BACILLARLE,
' From baculus (a staff).
These are much shorter than Synedra, and are found adhering together by one corner, in a zigzag manner, or free, like naviculse, gliding about in a drop of water. They are so abundant as to cover the confervse like felt.
Objects for the Microscope. 47
GOMPHONEMA,
From gomphus (a wooden peg),
is shaped like a wooden peg or wedge, and grows like a tree, on long filaments, attached to confervae or stones in fresh water, varying in shape, being sometimes round at the tip, or notched, or with a plain edge.
LICMOPHOKA, From lilcmos (a fan), a,ndiphora (bearing),
grows likewise on a stalk, but in dense masses, and is a marine diatom, parasitic on seaweeds. Its growth is dif- ferent from that of the Gomphonema. The stalk widens in the process of multiplication, and so spreads out the frustules like a fan.
RHABDONEMA,
From rhabdos (a staff).
These are marine also, and used as test objects, because, besides the striations, each frustule has two or four rows of marks called vittae. They were joined together when alive, forming a long tube ; but usually we only see the separated frustules here.
GRAMMATOPHORA MARINA, From gramma (a letter).
This is used as a test object to discover some very delicate striae on the borders of each valve, and is also remarkable for its vittae, which resemble letters ; especially this G. marina, which has four Greek gammas (y) on each frustule. The vittas are internal siliceous folds, and distinguish a large section of the Diatomaceae. There are fifteen species of Grammatophora. This one is found on seaweed in the Atlantic and Pacific oceans.
BIDDULPHIA, — AMPHITETRAS,
Biddulphia is one of the chain-like diatoms which adhere to one another by projecting angles, or horns. A band of
48 Objects for the Microscope.
minute cells forms a hoop round the valves, and when they multiply the young cells slip out from between the valves, and the hoop often becomes detached.
Amphitetras is a square cellular diatom, which frequently has its frustules piled up one over the other, with a large cell in each corner of the frustules. They are found alive in the sea off Cuba and the Canary Islands, fossil in Bermuda earth and Barbadoes deposit.
ISTHMIA ENERVIS.
A lovely diatom, found on seaweed on the English coast and in the Channel Islands. Its exquisite areolated struc- ture is very remarkable, and will repay careful examination. Its mode of increase is unlike all others. Two cells form within the valves, and as they enlarge break forth ; but still the siliceous hoop which once joined the new frustules to the old one remains attached for a time round one of them and alters its shape, causing some to appear truncated instead of round. The areolse of Isthmia are never well seen except with the parabolic illuminator, or mounted dry and viewed with a binocular microscope.
ARACHNOIDISCUS,
From araclini (a spider), and discus.
This beautiful disc is one from the guano, and is also found attached to seaweed ; especially one species, which is much used by the Japanese in making soup. It does, indeed, somewhat resemble a spider's web. But how can we describe the wonderful delicacy of its tracery, or cease to wonder at the perfection of its form, when we learn that this double disc has two inner valves ; the outer one horny, upon which are the web-like marks, is indestructible in nitric acid ; and the inner valve siliceous, suppbrts the upper one upon fretwork like a gothic window. This should always be looked at with a Lieberkuhn, or a parabolic illuminator.
Objects for the Microscope. 49
HELIOPELTA,
From Tielios (the sun), and pelta (a shield).
This diatom is found in Bermuda infusorial earth. We sometimes find two or three species on the same slide, and few mounted diatoms are as beautiful as the Heliopelta viewed as an opaque with the binocular. We then see the really raised compartments in relief, forming a five or six- rayed star of exquisite workmanship, with a striated margin and lateral spines, which are thought to connect the frustules together when in a young state. The number of rays de- termine the species. If the heliopelta has a five-rayed star in the centre and ten compartments, it is H. Leuwenhoekii. If there is a six-rayed star and twelve compartments, it is H. euleri. If there is a perfect Maltese cross and eight compartments, this is H. metii. But is quite necessary, in order fully to observe the structure, to have two slides of this diatom, the one for transmitted the other for reflected light, and the latter must have the Heliopelta mounted without balsam.
OMPHALOPELTA (CELLTTLOSA VEBSICOLOR).
This diatom so nearly resembles Heliopelta, that a little close observation is necessary in order to detect the differ- ence between them. The rays, though distinct, are less raised, and the margin has fewer spines, the rim is broader, and one species, 0. versicolor, has, with transmitted light, a play of colour from tawny to red, also a bright, clear, six- rayed star in the centre, and the rim, though narrower than 0. cellulosa, is very radiant. This is also found in Bermuda fossil earth, and other species in guano.
ACTINOCYCLUS,
From actin (a ray of light), and cyclus (a circle),
has no marginal spines, and from eight to ten divisions; is found alive at Cuxhaven ; fossil in Virginian earth.
50 Objects for the Microscope.
ASTEROMPHALUS ASTEROLAMPRA,
From aster (a star), omphalos (the navel), and lampra (shining).
Look for these in the slides of fossil guano, Bermuda earth, Virginia deposit, and Piscataway earth. They present beautiful umbilical rays, reaching only half way towards the margin, and alternate rays proceeding from the margin, forming a bright star in the centre, having five areolse in each marginal division.
COSCINODISCUS,
From coscinon (a sieve),
has no rays or divisions, but resembles the Indian turn of a fairy watch. The structure is wholly cellular, and the species, of which there are forty, are known one from another by minute yet regular markings, tubercles, and variations in the size of the cells. They are found alive in the sea off Cuxhaven ; fossil in the Richmond, Virginia, and Bermuda earths, also in the chalk marl of Oran.
These are the specimens most commonly sold by opti- cians, and they show us what Diatomacese are ; but to pursue the study, and learn the myriads which a little bog-water or a spray of seaweed would reveal, we must read Pritchard's work on Infusoria ; or, if further interested in the manner of their propagation, — which is really won- derful— read the article "Diatomacea" in the works on the Microscope by Carpenter or Hogg.
DESMIDIACE^l.
These are minute plants, of green colour, found in fresh water, shallow pools, and ditches.
YOLVOX GLOBATOR.
This is one of them, which, from its animalcule-like movement and extreme beauty, has long been considered as one of the Infusoria. If mounted, it may be beautiful, but is much more so in its living, moving state, in a drop
Objects for the Microscope. 51
of water ; revolving round and round, sometimes gliding along, sometimes rolling through the water, a transparent globe, enclosing from one to seven, or even twenty, lesser and darker green globules, of various sizes. Each of those globules in time breaks from its parent cell, and becomes likewise a mother plant, producing young volvoces with such rapidity that ponds are often thronged with them, and the water is coloured to a deep green. There is a pond at Blackheath which, in the months of July and August, abounds with Volvox globator.
CLOSTERIUM
is a favourite specimen of Desmidiacese. Its little half- moons, or ovals, sometimes joined together, are frequently found in all pools, especially on moors and in exposed places.
Lately the Closterium has been closely examined with high powers, and a circulation of fluid was seen throughout the cell. This requires a power of 300 diameters and care- ful management of light. Then a peculiar whirling move- ment may be distinguished in the large round space at the end of the cell, as well as along both the concave and con- vex edges of the Closterium. It is like the circulation in Vallisneria, Chara, and Anacharis, which I do not describe, because I am only noticing those objects which are mounted for students, in the hope of leading them to examine the living plants for themselves, with other books of a higher order. (Read ' Carpenter's Microscope/ chap, vi., on the Desmidiacea?.)
To find the Desmidiacea?, try small shallow pools, and not stagnant water.
The Closterium, Euastrum, Micrasterias, &c., will be found as a gelatinous stratum at the bottom, on stones, or stems of water-plants. The Staurastrum, Pediastrum, and all the smaller species, float as a thin film on the water, or form a dirty-looking cloud round the aquatic plants.
Raise the film with a small muslin net, or pour the water through your handkerchief, scrape off the deposit, and trans- fer it into bottles of fresh water for examination at home.
52 Objects for the Microscope.
If on plants, strip the stem with your fingers, and in the same way drop the gelatinous mass in water. Let it settle, and the little plants will flourish and remain long enough for you to study, not only their lovely forms, but also their manner of propagation, which is threefold. They multiply by self-division, by conjugation, or by zoospores.
The most common way is this : when a simple cell has come to its full growth, a partition forms in the middle, the cell gradually separates into two halves, each of which speedily becomes a perfect species of Desmidiacea.
The increase by conjugation, observed particularly in Closterium and Cosmarium, takes place thus : two fronds approach each other, and the outer cell-wall of each splits and throws out a connecting-tube which joins them together. Through this tube the contents of one cell is poured into the other, and mixing with the endochrome of the receiving- cell, forms a body called sporangium, which is afterwards set free by the breaking up of the parent cell.
Multiplication by zoospores has been observed in Cosma- rium, Pediastrum, and many others. The endochrome divides into a number of granular particles called gonidia, which escape through the cell-wall, and develop into per- fect cells.
Or they are ciliated and have a spontaneous movement, both in the parent cell and out of it, when they are called zoospores.
CONFERVA. — ZYGNEMA.
This is mounted for the microscope, as an example of conjugation amongst the Confervacese.
Confervacese are those plants which form the green or brown scum on ponds and ditches, and the long green, silky threads, that float in running water. Most beautiful are their ribbon-like filaments of varied pattern, and most useful their life on the stagnant water, which they purify by absorbing the noxious gases, and giving out the life- sustaining oxygen.
Looking at this scum for the first time will probably surprise us as much as anything. It does seem so won-
Objects for the Microscope. 53
derful that what we have passed by unheeded for so many years, or even turned from in disgust, should be so very beautiful. The filaments are worked by the hand of God in such varied pattern, that every pool may furnish us with a new specimen, and read us a lesson of the infinite care that has been bestowed on the lowest orders of creation.
The conjugation of Zygnema resembles that of Closterium, only as the filament is long and divided into many cells, every cell throws out a connecting tube, and one filament completely empties itself into the other, remaining colourless, whilst the recipient has a dark-green star of condensed endochrome in every division.
ACHTLA PROLIFEBA.
I have come reluctantly to the end of the vegetable slides, and upon each have said so little of all that there was to say that I can only hope my few words may prove very unsatis- factory, and so send the reader to better works and to the study of that open volume which lies around us, the hieroglyphics of which our microscope deciphers for us. Only one more little plant I will mention : it cannot be mounted, but you may raise it for yourself in a glass of water at any time. It is a parasitic plant on dead animal substances in water, and produces the zoospores of which we have been speaking. Throw two or three dead flies in a glass of water, and in a few days they will be covered with a cloudy film of minute colourless filaments ; that is the plant Acliyla prolifera.
I will describe what I saw the first time I examined it. I found one day in a small glass tank a dead larva of some aquatic insect, covered with a transparent mould, and on examining it with a half-inch object-glass, saw a mass of delicate white filaments. Some of these were filled with green granules in constant motion, and as I watched them the filament under observation began to expand into a club- shaped head, and the granules to form into small angular bodies, moving slowly round and round. The progress seemed so rapid, that I took out my watch to time the
54 Objects for the Microscope.
changes, which astonished me. It was a bright July evening.
20 min. to 7. The angular bodies were forming.
15 min. past 7. The gonidia, or zoospores, as I should call them, were becoming oval.
20 min. past 7. The gonidia were in violent motion, revolving and bounding against the end of the cell.
25 min. past 7. The end of the cell contracted and elon- gated, then suddenly opened like a beak, and out rushed the whole multitude of little zoospores, merrily swim- ming hither and thither, evidently ciliated, and always moving the small end foremost. The empty cell col- lapsed, and I forgot it in watching the other filaments, all progressing in the same way. The spores continued to move about rather more slowly for nearly half an hour, when the quasi animal life seemed to cease, and they floated away to germinate upon the nearest decaying substance.
I hope you will prove the truth of what I write ; it will afford much pleasure and a most useful lesson.
PART II.
OBJECTS FROM THE ANIMAL KINGDOM.
" The desire which tends to know The works of God, thereby to glorify The great Work -master, leads to no excess That reaches blame, but rather merits praise The more it seems excess ; For wonderful indeed are all His works, Pleasant to know, and worthiest to be all Had in remembrance alway with delight." — Milton.
THE slides usually prepared from the animal kingdom consist of insect parts, palates of Molluscs, Zoophytes, and miscellaneous objects, rather difficult to classify, since they seem to be mounted chiefly to please the eye of the purchaser.
The demand for " pretty objects " has been caused by the absence of any plan for the proper use of the microscope ; but now that we begin to find its real use, and appreciate its value as an educational instrument, the optician will have a better selection of slides on sale, and each object will be chosen as much for its usefulness as for its beauty.
There is a class of slides now sold by several opticians, which deserves especial recommendation. They are insects mounted whole ; one single preparation affording material for a day's study at least. Instead of isolated parts be- longing to unknown insects, we have the perfect body of Fly or Beetle, displaying its external anatomy, and giving us such an insight into its structure as we should hardly acquire with much reading and the best-drawn illustration.
Take, for instance, the slide of Scatophaga, or common Dung-fly, and read the description in this catalogue ; or the Telephorus Beetle ; and compare the two carefully in all
56 Objects for the Microscope.
their parts; reading at the same time, from Cuvier, or Westwood's ' Introduction to Entomology/ the generic characters of the Coleoptera and Diptera, and the young entomologist will have received a lesson never to be forgotten.
For those who have not begun the study of natural history, a few words are added on the classification of insects generally, without which some descriptions may be unintelligible.
Insects are so called from the word in-sccta, their bodies being divided into many distinct segments. They are a class of invertebrate articulated animals. The head is always distinct and furnished with antennae ; the body usually consists of thirteen segments ; they breathe by means of trachea? ; possess a nervous system, a circulation of blood, and a digestive apparatus varying with the necessities and habits of the species.
According to Cuvier's arrangement, insects are divided into twelve orders. The first four orders have no wings.
1. Myriopoda, example and
2. Thysanura „ Lepisma, or Sugar-louse
3. Parasita „ Pediculus (Louse)
4. Suctoria „ Pulex (Flea)
5. Coleoptera „ Beetles
6. Orthoptera „ Grasshoppers, Crickets
7. Hemiptera „ Bugs, Aphides
8. Neuroptera „ Dragon-flies
9. Hymenoptera „ Bees, Wasps, Ichneumons
10. Lepidoptera „ Butterflies, Moths
11. Strepsiptera „ Stylops
12. Diptera „ Flies
The objects themselves will be the best illustrations of these orders.
Preparations of animal tissues, blood, injected respiratory and digestive organs, and other objects relative to the physiology of the human body, are reserved tor a separate pamphlet.
Objects for the Microscope. 57
CHAPTER I.
OBJECTS FROM THE ARACHN1DA. SPIDER'S FOOT, JAWS, SPINNARETS, EYES, EPIDERMIS.
SPIDER'S FOOT.
THIS favourite object should always have three companions in its box — a preparation of Spider's eyes, Spider's jaws, and Spider's spinnarets, — therefore I shall say something of each of these, and also a little of Spiders themselves. W e are so familiar with them, so apt to dislike them in the house and overlook them in the garden, that it will be well to learn somewhat of their history.
Few persons realize the dignified position they hold in the order of creation. They are called insects; and are certainly not considered so aristocratic as Butterflies, or so
frand as the great Beetles ; perhaps a little higher than the ly they so cunningly ensnare. Therefore let us consider the Spider as a whole before we examine his foot.
The Spider is not an insect. It ranks higher than any insect, no matter how large or how beautiful ; and this on good grounds. In all God's works a perfect plan and regular order are established, and the organization of livipg creatures is gradually perfected, from the lowest form of animal life in the simple ciliated monad, up to the elaborate anatomy of man. Now the Spider might be an insect if we strictly adhered to the meaning of the term in-secta (divided into parts) ; but as its internal anatomy is more perfect, its respiratory apparatus, its circulation, and mode of reproduction, superior to those in any of the twelve orders of insects, the Spiders are called
ARACHNIDA,
and placed above them in natural order.
The Arachnida have oval or round bodies; the head, which is joined to the thorax, has simple eyes, which in
4
58 Objects for the Microscope.
structure more nearly resemble the animal than the insect eye. Sometimes there are eight, sometimes six, or only two. They have a mouth with jaws (maxillce], a tongue (iiyula), remarkable palpi, and frontal claws often of great magnitude. But the nervous system is the great distinction. The organ of sensation, which is the brain in man and animals, is a series of knotted nerves called ganglia in insects, from which proceed nerves to all parts of the body. The imperfect insect, such as a Caterpillar, has more ganglia than the perfect butterfly. And whereas the insect has generally from six to eight or ten ganglia, or little brains, in different parts of its body, the Spider has but two, and they more brain-like, more concentrated, and consequently of a higher order.
Then again as to the circulation : we know that in all creatures the blood is the life ; it is the fluid which nourishes all parts of the body. Not always red; it may be white, or yellow, or green ; but it is blood, and constituted more or less like our human blood, as the microscope reveals. All insects have a heart or dorsal vessel which pumps out the blood (as we shall see explained when examining the larvae of ephemera) that circulates loosely in the body, bathing the air vessels which supply it with oxygen ; but the Arachnida have a true heart ; long, indeed, like the insect heart, but furnished with arteries and veins which give it perfect circulation. This raises it another step higher.
The respiratory system is different in various species ; but the Spider whose foot we are looking at had lungs or pulmonary sacs, with two or four breathing orifices, situated just near the base of the abdomen, and inside those sacs a number of delicate white triangular plates which aerated the blood. This is more like animal respiration than the trachea of insects. (See Spiracles.)
The Arachnida do not undergo metamorphosis. The female lays eggs, making very pretty COCOOAS or nests for them, and the young Spiders come forth perfect from the shell, with the exception of the two fore legs, which are not always developed until a few days alter their birth.
And if we read any good work on the Arachnida we
Objects for the Microscope. 59
shall not fail to be struck with the intelligence of their habits and the amount of their instinct. For instance, in the structure of their habitations, one species (Clotho*) found in the south of Europe makes a beautiful tent in the shape of a cup, festooned at the edges, with the outer cover- ing of the finest texture, like taffeta, and weaves a second apartment, of still softer material, for her young. In this inner room, kept scrupulously clean, she hangs five or six little bags, wherein her eggs are laid enveloped in fine down. When she goes in and out of her tent she lifts the edge of a festoon and drops it again. The Mygale Spider, whose nest you may see in the British Museum, brought from Jamaica, is made of the hardest clay, having a trap- door fitting most exactly, and hinged with stout layers of silk ; the use of which she knows so well, that if it is half- opened by an intruder, she will pull it strongly inwards to defend herself.
The cunning and amusing way in which the Hunting Spiders catch their prey — creeping under a twig or window- ledge as gently as a deer-stalker, lying motionless for a while, moving as the Fly moves, turning with incredible swiftness round and round, ever keeping the prey in sight, until, quite certain of its being within reach, they spring like a Tiger, as fierce and as unerring in their leap.
We may watch these ourselves in our garden on a warm spring day, e.g. a little black and white striped Spider, called Salticus, which, before it leaps, cautiously fixes a good strong thread to the wall in case of a fall.
Again, we may see high instinct and deep affection in those vagrant Spiders of the wood, Lycosa3, which hunt with their cocoon of eggs so firmly clasped to the body that they will die rather than part with it.
A wise little Spider of our neighbourhood — its name I do not know — lives on the ponds and ditches of Otmoor, and spins a web round a kind of raft of Lemna, with a stem of grass or a little twig — to make it stronger, I suppose — and floats about on this, pouncing on any half-drowned or newly-hatched Fly which may come within its reach.
* Uroctea.
60 Objects for the Microscope.
Last of all that I shall mention, — as paper would fail me if I noticed all our spider friends, — is the Diving Spider of our aquariums (Argyroneta), common near London, rare in many parts of England : which has been taught to make a diving-bell for the work which God has appointed her. The water-world requires its avengers to keep down the fast- multiplying creatures therein, and the Aryyroneta aquatica is one of them. True her gill-like lungs enable her to breathe under water ; but still she requires more oxygen than it affords, and comes up about four times an hour for a supply of air. This she conveys to a silken house she has previously spun amidst the weeds in still water, and which we see shining like a little globe of silver ; the Spider halt inside, her breathing organs immersed in the air, and her head outside, watching for a tiny Beetle or a little Cyclops. For a more detailed account of the Water Spider, see ' Kirby and Spence's Entomology,' or the smaller work called 'Insect Architecture.' I only mention these facts to prove the reasonableness of the high position the Arachnida hold, and the unreasonableness of the neglect and dislike they often meet with. I bring them forward because the wrhole Spider is to be purchased beautifully prepared, and its external parts may thus be studied ; also because the comb of the foot is in every collection, and it is more interesting when we have some further knowledge of the body to which it once belonged.
The Spider's legs have a different formation from those of insects. Each has seven joints ; the two upper ones form a kind of haunch ; the next is the femur ; the fourth and the fifth are tibise ; the first or second according to the species, much the longest ; the last two are the tarsi, less distinct than those of insects, but remarkably furnished with toothed claws called the combs. In our Garden Spider, the Epeira, there are no less than five of these combs, besides three upper and untoothed claws, to each foot; also a strong moveabie spine or hook at the joint of each tarsus.
Objects for the Microscope. 61
The use of these combs is for cleaning itself and its web, the Spider being a most tidy creature. It has been seen to spend an hour or more in scraping the delicate threads of its web, when dust or soot had collected on them ; and if they were too thoroughly in crusted with dirt, these little claws broke the thread, rolled it up, and threw it away.
The combs have from fifteen to seventeen teeth, necessary for the swiftly running Spider when crossing the fragile web or twisting the silken bands that form its dwelling or its snare.
Whoever has patiently watched a Garden or a House Spider spinning its web, will have noticed how with these claws it shakes and tries the strength of each supporting line, and is able to cling to it or roll it up by means of these handy little combs, as well as to regulate the issue of the threads from the spinnarets, — as it were reeling it off.
SPIDER'S SPINNARETS.
These are not always well prepared. They are difficult to keep in position, but you could see them well by catching a good-sized Spider, and examining it as an opaque object. At the end of the abdomen you will find four or five teats or spinnarets, pierced with an immense number of minute holes, from which a viscid fluid, a kind of glue, exudes at the will of the animal, and is drawn out as a fine thread. In reality, each of those fine lines which we can scarcely see is composed of thousands of threadlets, for there are often 1,000 orifices in each teat. The fluid, first uniting from all these in one twist, descends about the tenth of an inch, and then twining with the three or four others, it becomes a cable in structure and in strength.
The formation of the web would be too long a process to describe here. Only one fact I add ; which is, that the Spider makes two different kinds of thread, and every web is fashioned of these different materials.
Take one of those common garden geometric webs, and throw a little fine dust against it. Look closely ; you will see that the dust adheres to the cross lines which form the circles, but not to the radii or supporting lines. This is
62 Objects for the Microscope.
because the Spider secretes a viscid matter, which she deposits in little globules all along each circle, and which acts as bird-lime in securing the prey. In one web of moderate size not less than 87,360 of these globules have been counted ; and yet the time occupied in its whole construction was only about forty minutes.
I often think that invalids, or mechanics, or town-people, who cannot enjoy many of our country pleasures, or learn God's wonderful ways in the instinct He has bestowed upon our humble fellow-creatures, might find much profit, much amusement, if they only knew a little more about the flies on their window-pane, and the spiders on the wall. And those careful housewives who so diligently sweep away this beautiful work, might leave just one sometimes, as a little page from God's Book of Creation, which, if rightly studied, would lead to happier thoughts than come with the over- carefulness about household matters.
I have said already that the eye of a Spider is of a higher type than the compound eye of insects. It has a single arched cornea, a spherical lens, and a concave vitreous body, with a cup-shaped retina and a layer of pigment cor- responding to the choroid membrane of the animal eye. It shines in the dark like a cat's eye, and evidently can see in the night as in the day. This is very remarkable, and de- notes higher organization than we find even in the aggregate lens of a Butterfly's eye.
The position of these eyes — for the Spider has six or eight — is admirably varied for their different habits and pursuits.
The Garden Spider, Epeira, has two very large red ones in front and two behind, forming a square ; two on each side almost confluent,
The House Spider has a double row of four each arching the forehead.
The Hunters have two fierce large eyes in front, four little ones just beneath, and two some distance behind, like watchmen or an "arriere-garde." Whilst the common
Objects for the Microscope. 63
Phalangia, or Harvestmen, which run always on the ground amongst moss and leaves, and are of the lowest rank in the society of Spiders, have but two eyes, seated on a tubercle or watch-tower on their back.
There are seventeen different positions at least in the eyes of those Spiders most common to us.
The jaws or chelifers of the Spider — properly speaking, the mandibles — are various in form, but always tremendous weapons, not only from their size and sharpness and the serrated edges and spines with which they are beset, but also because the upper joint contains a little sac of intense poison, which is emitted through a minute orifice in the next joint, and effectually kills whatever insect is bitten.
SPIDER'S PALPI.
The palpi, or feelers, serve as organs of taste and touch, and also as distinguishing marks of the sex. The male Spider has very large knobbed palpi, by which it is easily recognised.
EPIDERMIS OF SPIDER.
The skin of the Garden Spider (Epeira) is frequently mounted, and displays very beautiful undulating lines, surrounding the roots of the hairs. These concentric markings arise from the existence of folds in the inner membrane, beneath which lies a layer of pigment cells, to which the variegated appearance and beautiful colours of the Arachnida are owing.
The skin is merely washed, dried, and mounted in balsam.
64 Objects for the Microscope.
CHAPTER II.
INSECT PARTS.
TONGUES OF INSECTS. TONGUE OR PROBOSCIS OF HIVE BEE.
THIS is a common and favourite object in all collections, and very beautiful ; but it should always be one of at least five others in the insect division, in order rightly to appre- ciate and enjoy the exhibition it affords of adaptation for a particular purpose.
A moderate power gives a view of the whole tongue, so called, which in truth consists of several parts. The habits of the Hive Bee are well known, and need not here be described ; but it is worth observing how beautifully this organ is adapted for gathering the honey which lurks in the deep nectaries of such flowers as the Columbine or Honeysuckle.
Those strong-looking maxillae are chiefly used as pro- tecting sheaths for the delicately fringed and jointed ligula or tongue, which is stretched forth, having two feelers, called labial palpi, one on each side. These palpi are jointed at the tips, and used for steadying the proboscis in the flower-cup as it laps up the sweetness there. The ligula has forty joints, or more ; the number varies with the species ; you will easily see them with an inch lens. They render it perfectly flexible, as it sweeps round both concave and convex surfaces ; and with a tremulous lapping motion the fluid is drawn up along the hairy channel into the opening valve which protects its throat. There is a knob or kind of button at the tip, which has been falsely supposed to be a perforated sucker. The tip of the tongue is simply cartilaginous, but the base is hollow and capable of inflation to a considerable size. In this hollow part the nectar drawn from the flowers is collected previous to its passing into the honey stomach.
Objects for the Microscope. 65
If possible, the jaws or mandibles of the Bee should be mounted with the tongue, to show the instruments with which they fashion their waxen cells, seize their enemies, destroy the drones, &c. The mandibles vary in form and power with the different necessities of the species. The Hive Bee has simple spathulate jaws; the wild Humble Bee has toothed and stronger ones ; as also the Carder Bee, Mason Bee, and Carpenter Bee.
A comparative view of the tongues of these Bees would be most interesting, and for those who like to make a collection I will give the easiest way of preparing them for observation.
Soak the heads for about a fortnight in liq. potassse, to soften the skin and dissolve the fatty substance within, which prevents the parts from being distinctly seen. Then wash them in water, and press them flat between two pieces of glass until quite dry ; drop a little turpentine upon them and let them soak in it for a few days, when they will mount beautifully in Canada balsam. If bubbles of air remain in the tissue, lay the tongue on a glass slide, and cover it with a piece of thin glass; take a camel-hair pencil and drop turpentine between the glasses, which must now be suffered to boil over the spirit lamp, and the air will rush out in bubbles ; keep supplying turpentine until the object is perfectly transparent, then quickly and gently apply the balsam.
TONGUE OF WASP.
How very different this is from the tongue of the Bee ! Instead of the long and slender ligula, here is a short broad two-lobed membrane, far more useful to the Wasp, who does not trouble himself to collect the honey he will eat ready-made out of the comb, but who prefers rasping rapidly away the soft ripeness of the Peach, the Apricot, or the Plum ; or gnawing the juicy meat at the shambles, or sucking out the life of a fat Fly. This broad flat membrane —how handy it must be in making those curious paper nests wherein they rear their young ; a trowel and a smoothing iron, a spoon and shovel, as may be required ; and with
66 Objects for the Microscope.
those two brushes on either side ever keeping it clean and unclogged for its work ; whilst those four feelers, the labial palpi and maxillary palpi, ceaselessly vibrate over all, to ascertain the fitness of food or material.
There are many species of Wasps ; and some of them, especially foreign ones, feed more upon honey than do our common Wasps, and their lingulee are therefore modified for their wants, being longer and sometimes three-lobed, with a variation also on the mandibles or outer jaws.
These would make a very interesting collection prepared like the Bee's head.
BUTTERFLY'S TONGUE OR PROBOSCIS.
This is a beautiful piece of mechanism ; a long elastic coil which the hovering Butterfly throws lightly into the recesses of the deepest corolla. It cannot, like the Bee, dive down into the Honeysuckle or Campanula, or passion- ately tear open the nectary of a Foxglove. Its beautiful wings cannot fold so closely as to let it creep into the Salvia-cup or Lily-bell. Therefore its Creator gave it this excellent instrument adapted exactly to its wants. In the living insect it is coiled closely to its head, so as to be scarcely visible, and not at all to impede its movements. When unfolded, we perceive that it consists of two long tubes hooked together most curiously by minute teeth, which on either side are inserted into little pits between each row of teeth. Moreover each of these tiny teeth has a second tooth, which forms a deep notch, and prevents the accidental unhooking of this double tube. Then at the edge of each tube there are seventy-four little barrel- shaped bodies, or papillae, considered to be the organs of taste, and inside each tube, which you may observe is delicately striated, there are spiral vessels or tracheae con- nected with the larger tracheae in the head. Now the fluid does not pass up the interior of this antlia, which is its proper name, but is drawn upwards along that channel which is formed by the union of the two tubes. The papillae are best observed near the tip, and with a high power.
Objects for the Microscope. 67
PROBOSCIS OR TONGUE OF BLOW-FLY.
This is a true proboscis, but not so well seen alone if all its parts and uses are to be considered ; you should have the proboscis of a Gnat and of a Tabanus or House-fly rightly to understand the whole.
We see the little House-fly busy in our sugar-basin, or the Blow- fly, unwelcome in our larder. We feel the tire- some tickling on a hot summer's day when they gambol over our hands and face ; but we know not how beautiful is that little mischievous tongue. Here it is spread out, the simplest form having a broad fleshy lobe which is striated with spiral fibres, by which it obtains a sucking movement and draws up the juices it feeds on. Little short stiff hairs are set around it, and these are what do us mischief in rasping off the polish of our book-covers, and causing the irritation to our skin.
PROBOSCIS OF TABANUS.
This is the more complicated proboscis of the Tabanus, or Horse-fly. Who does not know how it torments our cattle, and the carriage horse in particular, in a dusty drive through the country ? A large brown Fly, with variegated wings, and such magnificent eyes ! She is easily caught ; for when she fixes on the horse and tastes the warm blood, her whole attention is given to the feast. I say she, be- cause the male Tabanus is found harmlessly hovering over flowers, and loves the haunts of the Honey Bee : his mouth has no lancets, whereas the female is supplied with very powerful instruments of assault.
The head should always be mounted with the proboscis, which greatly increases the interest of the slide ; because, although the eyes lose in preparation their gorgeous colour- ing of green, purple and gold, in zigzag bands across the facets, yet the delicate network remains, and shows the 4,000 meshes, which in life each contained an eye. As is the case with many of the Diptera, the eyes of the female are parted by a narrow band. Beneath the eyes, near the mouth, are the antennae, which are supposed to be organs of hearing, as they certainly are of feeling. Six-jointed
l>8 Objects for the Microscope.
these are ; the first and second bristly, the third is very long, and the last three very short. It is important to observe these things, as the shape of one joint in the an- tenna? will determine the species. In this very case, if we were examining the large and true Tabanus bovinus, we should see a very different third joint
Next let us examine the mouth.
That long and broad membrane is called the labium. Those lines at the inner edge of the two lobes are spiral muscular fibre, which enable it to lap or draw up the fluid it feeds on ; and those lancets are instead of jaws, or rather are modifications of the mandibles and maxilla?, which are the inner and outer jaws of insects. These lancets pierce the skin, and the labiurn sucks the blood of the horse. If the slide has the head of Tabanus bovinus, and not the com- mon Tabanus pliiviatih's, also called Ha?motopota, or "blood- drinking/1 the head will be armed with a strong pair of mandibles besides the lancets. The larva? of these flies live in the earth — long grey footless grubs, feeding, on decayed vegetables.
PROBOSCIS OF GNAT.
Here is another of our little tormentors, and a female Diptera also ; for the male Gnat dances gaily in the sun- shine with his beautiful plumed head, and has not by any means so well-developed a mouth. He does not suck blood, and probably sips a little nectar from flowers or the dew upon the leaves in the short time he has to live : the busi- ness of his life is to choose a mate and die. The female Gnat lives longer, and is very bloodthirsty. Here observe a long fleshy lip, or labium, which is the sheath containing two mandibles, two maxilla?, one labium, one ligula or tongue. They may not all be visible on the slide, as some may remain inside the sheath, and some may be broken off, they are so very delicate ; but if perfect it would show all these. The mandibles are finely toothed like a saw, but you require a quarter-inch glass to see this well. The ligula is shaped like a spear-head. The stiff horny labium is pointed like a needle. When the Gnat pierces the skin.
Objects for the Microscope. 69
the two serrated mandibles work rapidly up and down, the sheath folds backward, the pressure of the lancets causes a little poison-bag, situated at the base of the proboscis, to emit one drop of acrid matter, and when the little creature has sucked our life-blood, and her small body is distended and crimsoned with her draught, she flies off like a winged ruby in the sunlight, that little poison-drop rankling in the wound and causing our after uneasiness and irritation. It is worth the slight annoyance, however, to watch the process of her feast. With a pocket lens we can see the working down of the lancets, and the up-flowing of the blood into her stomach.
The shrill buzz of the Gnat, like a fairy clarion, is peculiar to the female, and only heard when she is bloodthirsty. Her delicate wings then vibrate 3,000 times in a second, and are supposed to cause this sound by the friction of their bases against her body. Her eyes, which quite cover her head, and the long fourteen-jointed antennae waving to and froj make her a beautiful object, in spite of her unpleasant propensities.
PROBOSCIS OF ASILUS.
The Asilus is one of the Diptera (Flies) — the largest and fiercest of them — most frequent in sandy situations. They flit about in the hot sunshine, pouncing upon all smaller flies — Beetles and Hymenoptera, Ichneumon flies, &c. — holding them between their fore legs, and plunging their sharp lancets and fleshy tongue into the softest part of their prey. The colour of these flies is mostly tawny, gold- coloured, or reddish-yellow; the wings finely-veined and clouded at the edge ; the body long and narrow. The larva lives in the earth : it has twelve segments, and changes to a spiny pupa, from whence the Fly emerges in June.
PROBOSCIS OF EMPIS-FLT.
The Empis is often called the Snipe-fly, from its remark- able labrum, which really resembles a Snipe's beak. When at rest it is folded close to the breast, but very frequently
70 Objects for the Microscope.
is seen transfixing the body of some poor smaller fly which the Empis is greedily sucking. The Empidae are generally small black flies, and there are many species of them. They are more fully described with the slide of Empis stercorea; also the peculiar veining of their wings.
PROBOSCIS OF DIOCTRTA,
one of the Asilidae, flies which inhabit meadows, trees and bushes, feeding on lesser flies, and more common than the true Asilus. They are usually black and shining, and carry their antennae very fiercely erect. The head should be mounted in profile to show the tubercle upon which the antennae are seated, five-jointed and porrect, close to each other at the base and diverging outward. The proboscis stands out almost horizontally.
HEAD OF COXOPS.
This is a pretty black and yellow Fly, frequenting flowers, having a bright triangular spot on the top of the head. The thorax with two yellow scapulae, and the abdomen is banded black and yellow. The remarkable part of the head is a singular proboscis curved suddenly upwards ; a labrum notched at the tip, arched above and hollow beneath ; labium bilobed and slightly hairy, with three shallow transverse furrows at the tip. The antennae should be well displayed, for their structure alone would determine the species, and therefore furnish a useful lesson on the absolute necessity of minute observation, if we wish truly to learn and enjoy the insect world.
The antennae of Conops are about as long as the head, fiercely seated on a tubercle, and have seven joints ; the first, short and slightly hairy, forming an angle with the second, which is much longer and rather club-shaped : the third is seated on the second like a cone, and the fourth is very small ; so is the fifth, and the others are like little spines ; nevertheless they are seven in all. The eyes are prominent and oblong ; but the eye of the Ely is particularly described in the head of Rhingia.
Objects for the Microscope. 7)
HEAD OF RHINGIA, OR SYRPHUS.
This beautiful preparation is the one I have chosen for drawing particular attention to the eye of the Fly. That fine delicate lace, now perfectly transparent, is the skeleton or framework in which were set four thousand perfect organs of sight, which we call the eye of a Fly. That outer mem- brane, which is all that is now left, is the cornea ; it was lined with an intense black pigment, excepting one tiny spot in the centre of each facet, through which the light was admitted. Behind the pigment was a broad zone, orange-coloured and black ; then a second zone, deep blue or black ; then the optic ganglion, gathering all the fila- ments of each eye into one knot — the brain.
The brain of insects is not a solid mass, or great ganglion, like the brain of animals ; but the medium of communica- tion between insects and the external world, is a nervous system consisting of two medullary threads or cords, and a series of knots or ganglia placed at intervals throughout the body.
Larvae have usually two of these ganglia to each segment of the body. The perfect insect has fewer ; but the first ganglion, as in the Fly, always sends out the nerves of the eyes, tongue, maxillae, mandibles, and antennae. Therefore we understand how the organs of sight are united in the head of a Fly upon the first ganglion or brain. And whilst each eye receives a perfect image of the object before it, one single impression may be conveyed to its possessor.
This head of Rhingia has also a very beautiful tongue, long and slender, lobed and edged with spiral fibre, capable of great extension to accommodate the habits of the Fly.
The Rhingia campestris, or Rostrata, is so called from its projecting horny beak. It is a very pretty Fly com- mon in woods and gardens during the summer ; remarkable from its hovering like a Humming-bird over the flowers, and darting suddenly into them, sucking the honey-drop with this long and slender ligula, and then out again with a swift jerking flight not very easily followed. Its body is a dull red ; the wings finely veined, like all its family, the Syrphidse.
72 Objects for the Microscope.
HEAD OF DRONE-FLY, OR HELOPHILU8.
This^so nearly resembles the Rhingia that little need ^ added in explanation, except of the fly itself, which is one of the Syrphiclse, nearly related to the Rhingia. The Helo- philus is that large black and yellow fly so common in the autumn on Michaelmas Daisies, often mistaken for a Wasp, as it makes a loud humming noise and is very intent upon its feast. It passes through a greater change than most of the fly tribe ; for it lived and fed in the foulest sewer as a rat-tailed larva which is very curious in its manner of breathing. This larva has a long retractile tail, with the action of a telescope, capable of immense extension to reach the surface of the water or mud for air. The body being very transparent, the trachea! vessel is distinctly seen in a wavy line the whole length of the tail.
HEAD OF ERISTALIS,
differs only from Helophilus in having a black hairy body, more like a Bee. The antennae are very beautiful.
HEAD OF TIPULA.
This favourite and beautiful preparation is the head of our familiarly called Daddy-long-legs. The colour adds to the beauty of the lacework eye, and the fine antennae, simple yet varied in the length of the joints, which are each slightly hairy. The palpi have four joints, and bend over the broad fleshy proboscis, in which large trachea are distinctly seen. These Tipulse are very destructive in the grub state. The female deposits her eggs in deep burrows by means of a long ovipositor, consisting of four pieces ; two of them bore like an auger the required hole in the earth, and the other two join and conduct the egg to its appointed place. When the larva hatches it has two short horns on its head, several fleshy conical appendages on the abdomen, and two very strong mandibles working against two horny convex dentated plates. Very destructive are they to the farmer's grass land, often destroying hundreds of acres in England and France. The more, therefore, of these beautiful heads that are thus prepared the better.
Objects for the Microscope.
HEAD OF LIMNOBIA.
This is essentially like the head of Tipula. I need only say that Limnobia is one of the same family, only of a different genus, and the larvae are much less destructive, living mostly in fungi.
HEAD OF HEMEROBIUS.
This is usually mounted as an opaque object, to show the metallic lustre of the eyes. The Hemerobius belongs to the order Neuroptera. Is has four exquisite light green wings resembling delicate lace, and lays its eggs on the twigs of lilac trees; these eggs are stalked and placed in rows along the twig, from which a very useful little larva emerges— a destroyer of the Aphides.
HEAD OF PANORPA.
The Panorpa is called the Scorpion-fly, and is very common on nettles in the middle and end of summer. They are not difficult either to distinguish or to catch ; for the male fly is very conspicuous with his long turned-up tail, at the end of which he brandishes an unpleasant- looking pair of forceps. The wings, four of them, are highly reticulated, which denote it to be of the order Neu- roptera, and first cousin to the beautiful Dragon-fly and brilliant Hemerobius ; they are prettily spotted, and of equal size. If we look at the head we shall see a pair of long antennae inserted between the eyes, three ocelli, or little eyes on the crown of the head, and this long snout-like proboscis, with mandibles, maxillae and lower lip nearly linear, and four or six short palpi. Upon this beak we often see a little insect spitted, whilst the tongue is rapidly sucking out its life's-blood. The Panorpa is a carnivorous fly, and hunts in the hot sunshine, not only on the wing, but running swiftly under and over the nettle-leaves, intent on his pursuit, and easily captured himself whilst thus engaged.
5
74 Objects for the Microscope.
TONGUE OF CRICKET.
(Acheta.)
This is an example of a true insect tongue, and must be examined with several powers if we wish to see all its beauty. For a general view use an inch lens, and observe the two strong muscles which move it, from whence nume- rous fine spiral fibres arch over the transparent membrane. Afterwards use the half-inch and the quarter-inch, when these fibres appear to be furrowed or fretted, like little files, and must form a most useful tongue for the voracious Cricket. We all know how destructive it is in the house ; gnawing linen or books, or feeding on flour, meat — in short, anything it can find. After this tongue has performed its office, there is a complicated gizzard, which will be explained in its proper place ; though it ought to be looked at after the tongue, and with the wing-case of the male Cricket, whose drum and file is a very interesting micro- scopic object.
The House Cricket belongs to the order Orthoptera, or straight-winged insects. The female does not chirp ; she is known by a long pointed ovipositor, with which she deposits about 300 eggs in a season.
GIZZARD OF CRICKET.
This is a most interesting object in connection with the tongue of the Cricket, as illustrative of the digestive organs j>f the Orthoptera. It is usually mounted in Canada balsam and viewed with transmitted light ; but the effect is more beautiful, and the structure better displayed, by examina- tion with the parabolic reflector, or a simple Lieberkuhn, when the scale-like plates are thrown into relief, and the formidable apparatus for digestion is manifest.
The Cricket has a long and dilatable oesophagus, which ends in a crop or sac for the reception of food in a rough state, and this is followed by a gizzard, consisting of two skins, the inner one plaited into six folds having longitu- dinal rows of teeth resembling toothed scales, the outer row much smaller than those in the centre, and each
Objects for the Microscope. 75
capable of elevation and depression. The whole grinding machine is moved by thousands of muscles, which enable it to reduce the food to a pulp, and it is then passed on to the intestinal canal or lower stomach, where biliary vessels, analogous to the liver in the higher animals, pour in the bile, which finally prepares the food for the general nourish- ment of the body.
A most interesting collection of gizzards may easily be made, and the variation and adaptation of structure observed, by preparing the stomach of Dytiscus, of the large Grasshopper or Locust, the Cockroach (Blaps), Tene- brio (Beetle) and most of the predaceous Beetles. One small Beetle, a wood-borer, Cryptorhynchus lapathi, has a gizzard so minute as hardly to exceed a large pin's head in size, and yet it is said to be armed with no less than 400 pairs of teeth, moved by a far greater number of muscles.
MOUTH OF BEETLE. (Telephora, or Soldier-beetle.)
This is a common and favourite object, and should be considered carefully, for it belongs to that large and useful tribe of insects which we could no more spare from their place in creation than we could the flowers of the field, or the birds of the air.
A Beetle's mouth will be more interesting if we say a few words about the Beetles themselves.
Coleoptera they are called, from two Greek words, signi- fying " wings in a sheath." No less than 30,000 species are known, of which 3,600 are found in Britain ; exceeding the amount of all our other native animals, and forming a third part of our insect population. They vary in size from the great Prionus, which measures six inches long, and has nine inches expanse of wing, to the minute Trichopteryx and Atomaria, hardly one-eighth of a line — quite micro- scopic ; and yet every external joint, every internal organ, is as perfect in the small as in the large.
The usefulness of the Beetle tribe is far greater than is imagined. Not only in the perfect state do they remove dead animal substances, excrements, &c.,but in their larval
76 Objects for the Microscope.
state feed on decayed vegetable matter, which else would render the air unwholesome for our existence, and more offensive to our senses than can well be imagined. Let us examine, therefore, the mouth of our little scavenger.
It has six parts. An upper lip, called labrum, which covers the mouth, and is horny or leathery, but simple in form.
Two upper jaws, 'called mandibles, varying in shape, but strong and toothed, or hooked, for seizing their prey and tearing it to pieces before it is passed on to the more deli- cate under jaws or
Maxillae, which are fringed with delicate hairs, and to which are attached jointed palpi, or feelers. The tips of these are often triangular, or hatchet-shaped, which will distinguish them for your observation. These palpi move very rapidly, apparently examining the food, and two others are attached to the under lip or
Labium, for the same purpose. Part of the labium is called the chin or mentum, usually having a notch in the centre. Some of the Beetles have a distinct tongue inside all this — the Dung-beetle for instance— lying between the labium and labrum. It is a simple membrane, sometimes fleshy, sometimes horny.
The mouth of a Beetle would be much better examined by taking a large Beetle, and soaking the head for a few days in liquor potassaB ; then washing it in a watchglassful of water, when the parts are easily separated and studied. Do this, because from one mouth we cannot learn all that is useful or interesting. For instance, in the mandibles are found different kinds of teeth ; molar teeth for grinding food, or incisive teeth for tearing it. The maxillae also vary extremely in their form and appendages. The lobes are often furnished with spines or teeth, and are single or double, fringed or plain ; but the predaceous Beetles have always fringed lobes like stiff brushes, as if for cleansing the food or the other appendages of the mouth. Also, I may mention that the palpi of those Beetles which feed on the pollen of flowers, such as the tribe of the Nitidu- sidce, are used by them to open the anthers in a very curious way.
or the Microscope. 77
The antennae of the Beetle are not described here but in connection with those of the Blow-fly and Bee, concerning which some interesting discoveries have been lately made.
MOUTH OF BEETLE.
(Bouche et palpes de Calatlius Castelloides.)
This is a black Beetle about half an inch long, very common in the neighbourhood of London ; found under stones.
The object is good as showing beautifully fringed maxillae with two pair of labial palpi ; the outer pair have four joints, the lower pair only three. Some species of Coleoptera have one pair of labial palpi, and one pair oi maxillary palpi.
Observe, the little tonguelet in the centre has two ear- like appendages, called paraglossse. That broad curved plate above it is the men turn, with a notch in the centre, which distinguishes the section of the Carabici to which it belongs.
MOUTH OF BRACHINUS.
(Bouche et palpes de Bracliinus.)
The mouth of the Bombadier Beetle (see leg of Brachinus), one of the Carabici, which has the maxilla? terminated simply in a point ; the tonguelet exposed, and labial palpi distinctly three-jointed ; the mentum not toothed ; the last joint of both maxillary and labial palpi evidently dilated.
MOUTH OF ONTHOPHAGUS. (Bouche et palpes.)
One of the Dung-beetles or Scaraboeides, the earliest species of the spring. It belongs to the large family of the Lamellicornes, having the antennae clubbed and composed of leaflets arranged like a fan, opening and shutting in the same manner. The first pair of legs are remarkably strong, the tibia? toothed for burrowing in the earth and manure upon which they feed. Many of the species are very large and beautiful, with metallic bodies and sculptured Elytra. The Onthophagus is small, but of a brassy black colour ;
78 Objects for the Microscope.
the elytra dull grayish-yellow thickly clouded with black, and it has a curious pair of horns on its head. The mouth shows a pair of broad curved and delicately fringed maxillae, which deserve examination with a high power. The last joint of the maxillary palpi is the largest, and the labial palpi are very hairy.
MOUTH OF ANCHOMENUS,
a species nearly allied to Brachinus, a small green Beetle found under stones. We observe the maxillae terminate in a single hook, with two pair of palpi, and the tongue- let having the paraglosssa mentioned in the mouth of Brachinus.
MOUTH OF CRIOCERIS.
(Asparagus Beetle.)
This abundant and pretty Beetle is found in the hot sunny days of July laying eggs upon the asparagus plants. It is blue and red, with the elytra marked in the form of a double cross, yellow and blue. It belongs to the order Tetramera, having four joints in the tarsi.
The mouth displays a membranous two-lobed tonguelet, the maxillae whitish and membranous, delicately fringed ; the terminal lobe straight, the palpi filiform.
MOUTH OF LADYBIRD,
(Coccinella,)
too well known to need description ; but it may be noticed that it belongs to the last order of Coleoptera, the Trimera, having only three joints in the tarsi.
The mouth is very remarkable from the hatchet-shape of the last joint of the maxillary palpi. The maxillae are armed on the inner edge with a horny tooth.
When the Coccinella is alive and in its youth, the circu- lation of blood may be seen in the veins of the wing.
MOUTH OF STENOPTERUS RUFUS.
A black Beetle with red antennse, not common in Eng-
Objects for the Microscope. 79
land ; found in June near Darenth Wood and Coombe Wood. It is one of the Cerambycidse, a section of the Longicornes. These have only four joints in the tarsi, the last three furnished with short brushes, and the first and second joints heart-shaped. The mouth is very differently constructed from those before described. The two maxillary lobes are remarkably distinct and prolonged beyond the palpi : the last joint of the palpi thick, conical, and dark- coloured. I may mention here, as Stenopterus is rare in England, that a very pretty species of the same family may be readily found on willows, and the mouth will show the same kind of maxillae, with this one difference in the palpi —that the maxillary palpi are very much smaller than the labial, or even the maxillary lobes.
The beetle to which I refer is Cerambyx moschatus, or Musk-beetle, about an inch long, green, shaded with blue, or a more golden colour, emitting a scent of musk or of otto of roses on being handled. It has long antennae, and kidney-shaped eyes surrounding the base of the antennas. The larva is a soft white maggot, burrowing under the bark of trees.
A N T E N N JE.
The antennae, or feelers, are very important organs in all insects ; but especially in the flies and beetles. In both these orders the shape, position, and number of joints in the antenna?, form distinguishing characters in the genera and species of insects.
They are situated on the head, near the eyes. They deserve particular attention and study ; for no organs are more wonderful or more useful, and, until lately, none so little understood. The order Coleoptera is divided by them into the families, Lamellicornes, Clavicornes, Serri- cornes, and Palpicornes. For examples of these, which are very beautiful, look at the head of the common Dung- beetle, which has a clubbed antenna, formed of leaflets, capable of being shut up.
80 Objects for t/ie Microscope.
ANTENNA OF COCKCHAFER,
another Lamellicorne beetle, every leaflet of whose beautiful antennae shows a cellular tissue of oval cells, with nucleus and nucleolus, according to Quekett ; but with an external cuticle of hexagonal cells, according to Carpenter. The organs of sensation, sacs and sacculi, are found in them, and occupy the place of the nucleoli of Quekett. (See antennae of Syrphus.) The leaflets of the male are much longer than those of the female.
ANTENNAE OF NITIDULARIA.
An example of Claricorne antennae. These Nitidularia are small beetles which haunt our flowers and swarm upon nettles all the summer long, and may be recognised by their antennae having eleven joints, the last three clubbed.
ANTENNAE OF HYDROPHILUS,
is an example of Palpicorne antennae ; clubbed also, but differently shaped, and having only nine joints — never more.
ANTENNAE OF ELATER.
Here is a common little beetle, often called Skip-jack, from its springing up with a jerk when laid on its back ; easily recognised on plants by its depressed head, and long dark body; also by its habit of falling down as if dead when alarmed. The antennae are an example of the Serricornes, toothed or serrated, especially those of the male insect.
For examples of variety of antennae in the Diptera, look at the heads of Dolichopus, Empis, Sepedon, and Syrphus, Phora, Tabanus, &c. Compare these with the antennae of Bee, Saw-fly, Ichneumon-fly, and Dragon-fly. The antennae not only vary in the species, but in the sexes, and are always most beautiful in the male ; as in the head of a Gnat, which is plumed, whilst that of the female is quite plain.
The wild Bees, Saw-flies, and Beetles, present many examples where the different shape and length of the
Feet of Insects, Petal of Geranium, etc.
Plate 3.
1. Foot of Spider magnified 18 diameters. 2. Claws of Spider, magd. 100 diams.
3. Foot of Fly, magd. 20 diams. 4. Foot of Boatfly, magd 4 diams. 5. Boatfly. 6, Boatfly floating 7- Boatfly on the wing. 8. Petral of Geranium. 9 Piece of Geranium Petal, magd. 8 diams. 10. Minute portion of Petal, magd. 150 diams. Pollen of Olarkia pulchella, magd. 100 diameters. 12. Pollen of Crown-imperial, magd. 100 diams. 13. Grain of the above, magd. 300 diams. 14. Pollen of Salvia patens, magd. 100 diams.
Objects for the Microscope.
antennae enable us at first sight to recognise the sex. Therefore we should study them, especially in the following
i t-i o r\ r* 4- ct •
insects : —
|
WILD BEES. Chelostoma Specodes Halictus Andrena Eucera |
BEETLES. Cerambyx Anthrenos Colymbetes Scolia Anthrophila |
Rhipicera Chelonus Elater |
MOTHS. Bombyces Saturnia |
|
ICHNEUMONS. Pteronus |
It has been supposed that they were chiefly the organ of touch, probably of smell also, and of hearing. Certain it is that they are most important to the insect, and that special contrivance for their preservation and use may be observed in many tribes. I will but mention a few exam- ples. The common Water-scorpions, Nepa and Belastoma, have very deep kidney-shaped boxes between the eye and the throat to defend their singular antennae. Cryptocerus, a remarkable ant, has a square plate,, the sides of which form a longitudinal cavity in which the antennae lie quite concealed and safe. Many of the Diptera have furrows in their foreheads, which receive and protect the antennae in repose. Many beetles, Anthrenus and Byrrhus, have cavi- ties under the prothorax or breast, where, when alarmed, their antennae are secreted.
But in proof that they are certainly organs of sensation in a high degree, it has lately been discovered that the antennie of Bees, Wasps, Flies, Dragon-flies and Ichneu- mons have peculiar structures which had never been described before. Dr. Hicks published his papers on the subject in the ' Transactions of the Linnaean Society, 1857.'
ANTENNA OF SYRPHUS, OR OF BLOW-FLY.
(Muscat, Vomitoria.)
Either of these may be taken to illustrate what is stated by Dr. Hicks. If properly mounted they will be trans- parent ; and on the third joint of each example will be seen a multitude of transparent dots. These dots are perfora-
82 Objects for the Microscope.
tions of the inner coat of tke wall of the antenna, closed externally by a very thin membrane. Behind this perfora- tion is a sac which, when the antenna is crushed or broken up, may be found floating about in the fluid. There are about 17,000 of these sacs in each antenna. Besides these simple sacs there are large spores, which lead into chambers from which numerous little sacs or sacculi radiate. These apertures are fringed with very minute hairs. There are about eighty of these cavities on each side of the antennae. They are filled with fluid, closed in from the outer air by a very thin membrane, and to each little sac a nerve proceeds from the large antenna! nerve. This will be seen better in
ANTENNJ3 OF BEE.
On the last three joints of these antenna, but only on one side, we find these vesicles or sacs j and if properly pre- pared the great nerve may be distinctly seen, giving off three bundles of finer nerves, each of these dots receiving one.
ANTENNAE OP ICHNEUMON.
One species of Ichneumon will give singularly-shaped perforations, in which the transparent membrane over-arches and extends beyond the aperture, and gives it the appearance of an inverted canoe.
ANTENNA OF ARGYNNIS.
Argynnis, or Fritillary Butterfly, tawny coloured, with black lines and spots on the upper wing, and silvery streaks and spots on the under side of the hind wing. The antennae possess small transparent dots and chambered cavities.
PALPI OF ARGYNNIS,
a very pretty object, showing the scales or feathers of the Butterfly in situ.
ANTENNA OF DRAGON-FLY
furnish the most beautiful examples of these, acoustic cham- bers, and display the nerve well.
Objects for the Microscope. 83
ANTENNA OF SILKWORM MOTH.
These will form an example of the variation of the An- tennae in the sexes, those of the male Moth being pecti- nated throughout equally, while those of the female have shorter branches, and alternately one long and one short.
To prepare the antennaB of Bees, Wasps, and Flies, for these observations, it is necessary to soak them in chlorate of potash, with a few drops of hydrochloric acid, until they are colourless ; then dry them and mount in balsam. .
SPIRACLES AND TRACHEAE. SPIRACLES OF DYTISCDS.
The Dytiscus is a large Water-beetle, very common in ditches and ponds, belonging to the pentamerous Coleop- tera. It passes its first stage of existence wholly in the water as a most voracious larva, with long narrow body and strong head, armed with mandibles, breathing by the anus, and rising frequently to the surface, when it hangs head downwards and the body curved like an S. When full-grown as larva it buries itself in the earth, changes to a pupa, and afterwards to the perfect insect. It is from the Beetle that these spiracles or breathing organs are taken.
Few objects are more beautiful than those prepared from the respiratory apparatus of insects. The blood of insects is aerated, not by its passing through particular organs, as the lungs in some land animals, or the gills offish ; but the air is circulated in every part of their body by means of delicate spiral vessels, called tracheae, or air-tubes, which ramify into the minutest organs. As you observe these spiracles, look also at these slides, which are very commonly found in all collections.
TRACHEA OF DTTISCUS.
You see they greatly resemble the spiral vessels of plants ; within the outer membrane an elastic fibre winds round and
84 Objects for the Microscope.
round in close and regular coils, and then comes another thin transparent membrane, closing it in and securing it from disturbance. When these tubes are pressed flat and are large, as the trachea of Dytiscus, then the double wall of fibre crossing each other gives an appearance of watered silk. Vessels such as these in the tongues, wings, and throughout the body, are easily dissected for examination, by opening the abdomen and floating off the fine white threads which branch off on either side from every spiracle. This brings us back to the spiracle itself, which is on every segment of the abdomen, an oval opening defended by those beautiful arborescent hairs, preventing dust or particles of harmful substance from entering in and lacerating the delicate tracheal vessels.
SPIRACLES OF COCKCHAFER. (Melolontha.)
Here is a difference of structure in the spiracles of the larva of Cockchafer, which burrows in the earth to a great depth, and whose naked body has no defence for its tracheal aperture ; therefore the spiracle, though very small, is doubly protected by a framework of bars, stretched from side to side of the thickened margin, and a membrane dotted with minute holes covers these again, effectually protecting the trachea?, whilst it freely admits the air.
SPIRACLE OF FLY,
is a modification of the spiracle of Dytiscus. It is inter- laced with branching fibre.
SPIRACLE OF TIPULA.
This has a solid disc in the centre, and radii proceed from thence to the margin.
SPIRACLES OF WATER LARY^l.
These are best examined in the living larvae of the Gnat, where the last segment of the abdomen is prolonged into a tube, the mouth of which remains at the surface of the water whilst the animal breathes.
Objects for the Microscope. 85
There are, however, other and quite different modes of respiration in aquatic larvae, which form beautiful micro- scopic objects.
AERATING LEAFLET OF LIBELLULA,
the larva of one of the Dragon-flies, those slender, beau- tiful blue and scarlet flies, which glance like living sun- beams across our path on a summer's day, and may be found in thousands resting on the reeds and bushes at the river's side. When these are in the larval state, they have three leaflike plates at the extremity of the abdomen, over which innumerable tracheae ramify and draw from the water that supply of air which is needful for their life.
ABDOMEN OF EPHEMERA, OR SPIRACLES.
The larva of the pretty May-fly, or Ephemera, has on either side of its body a row of little leaflets, each of which is an external spiracle, and when alive it is most interesting to watch its palpitations, the play of those tiny organs drawing oxygen from the water to aerate the blood. It is best thus to see it, because we are able to observe the circulation of the blood through the transparent skin.
CIRCULATION OF BLOOD.
All creatures that have life have blood : it is the nourish- ing fluid which is needful for existence. In insects, it is colourless, but composed of minute corpuscles, which are propelled through the body, not by arteries and veins, but by one great dorsal vessel, constricted at intervals, and one end of which is closed, the other open and acting as the aorta of the heart. We see it here constricting and dilating, pumping out the blood which bathes the whole interior of the body, flowing into the antennae, the legs, the wings- taking all directions. Here also we see a regular current through each appendage of the tail, and backward it is drawn into the long dorsal vessel through some lateral fissures in it, which are closed by valves, preventing its return. More- over, we can see in this larva the constrictions of the heart,
86 Objects for the Microscope.
its divisions into parts or chambers, called cardiac chambers, each of which is closed by a little door or valve, only opening upwards, so that the onward flow of the blood is secured, and out it is forced from the aorta again to con- tinue its circulation. We understand better when we have watched this in the living creature, how the delicate tracheal vessels receiving air through the spiracles give it out to the blood in which they are immersed. Although there are no distinct membranous veins in insects, yet the blood flows in regular channels formed by the interstices of the flakes of fat, air-cells, muscles, &c. The pulsations vary in different insects. Hunter counted thirty-four pulsations in a minute in the heart of a silkworm ; which we can do, as the great dorsal vessel is very distinctly seen constricting and dilating in the full-grown larva. When excited by fear or muscular exertion, the action of the heart is accelerated to as many as 100 and 140 pulsations in a minute.
In examining the larva of Ephemerae, which are abundant in most ponds, simply confine it in a live box with a drop of water, and just press it sufficiently to keep it still, yet unhurt. If you cannot easily find a larva of Ephemerae, any waterbutt in summer will abound with larvae of Gnat, and they will do nearly as well. So also will a newly- hatched Fly, or a young Bee, just before it emerges from the pupa case ; in these the circulation will be observed in the wings.
SPIRACLES OP LARVA OF BOT-FLY. ((Brfrw.)
See egg of (Estrus for an account of the Bot.
WINGS OF INSECTS.
There is much to learn in the wings of Coleoptera, Hemiptera, Hymenoptera, and Diptera. The scales or feathers which clothe the wings of Lepidoptera are noticed under Scales of Moth. The Diptera are classed by the veining of the wings, and therefore it is absolutely necessary to have a few specimens mounted as lessons for the names of the nerves or veins of the wing.
Objects JOT the Microscope. 87
The wing itself may be described as a transparent mem- branous organ, consisting of two laminae, or plates, which are united by canals called veins or nerves. These veins are hollow channels through which the circulating fluid flows, and a tracheal vessel runs in communication with the tracheae in the thorax.
In the Ladybird's (Coccinella) wing, the blood is not con- fined to these canals or veins, but circulates freely through a large part of the wing. The circulation may be seen in the wing of any newly-hatched fly, but especially in that of the beautiful lace-winged fly, Hemerobius, where it was first noticed by Dr. Bowerbank.
WING OF SCATOPHAGA.
Although this is fully described for the slide of Scato- phaga, mounted whole, it is mentioned here as the best lesson on the veins, and very easily put up separately. If merely mounted dry, the veins are sufficiently seen, but when soaked for a few days in turpentine and mounted in balsam, they become transparent from the expulsion of the air ; and then not only the canals, but the trachea?, may be visible, especially in the costal vein.
Observe that strong vein bordered with hairs on the fore-margin of the wing— that is the Costal vein ; and in the Coleoptera there is inside a little bag of fluid called the Phialum, by which the fly can, at its pleasure, increase the weight of its wing, and sink or fly slowly.
The short vein next to the Costal, ending at about one- third of the length of the wing, is called the Sub- Costal.
The next to that is the Mediastinal.
The next is the Radial, which forks off at its base ; and the farthest branch is the Cubital, always an important vein.
After the Cubital comes the Prcebrachial, joined to it by a transverse vein, called the Discal transverse.
WING OP HOUSE-FLY.
(Musca.)
This is an example of the true fly's wing. The Muscidse are very numerous, and divided into many groups and
88 Objects for the Microscope.
families ; the third joint of the antennae, always the largest in this family, enables us to recognise a true Musca at once. After that we must look at the wing, which varies very much in the number and position of its veins.
There are many house-flies. The Musca domestica will show the prsebrachial vein, forming a rounded obtuse angle at its flexure, nearly straight from thence to the tip ; the discal transverse vein nearly straight, parted from the border by more than half its length.
This little wing makes 600 strokes a second, carrying it five yards ; if alarmed, can increase its velocity to thirty- five feet in a second.
WING OF BLUE-BOTTLE FLY,
(Musca Vomitoria,)
will show the Discal transverse vein with two distinct curves, parted from the border and from the flexure of the prsebrachial by hardly one-third of its length. The an- tennae of this fly have the third joint remarkably long, and furnished with peculiar organs of smell. (See Antennae of Blow-fly.)
WING OF SYRPHUS,
not one of the Muscidse, or true flies, and therefore a good example of a beautiful variety. The Syrphidse are a nu- merous family, comprising thirty-one genera; they are mostly seen hovering over flowers, vibrating their wings as they pause awhile, then darting with rapid flight a short distance only, and becoming stationary again. Many of the species make a humming noise like a Bee, and are mistaken for either Bees or Wasps.
The veining of this wing is an excellent lesson. The Costal vein ends just before the tip of the wing, and receives the Radial, or Cubital; for both these veins are not always present in the Syrphus wing.
The Mediastinal is very distinct ; a transverse vein con- nects the Cubital with the Prcebrachial near the margin. But the chief distinction lies in one or two spurious veins,
Seed-vessels of Ferns, and Section of Limestone.
Plate 2.
I. Seed-vessel of Fern when unripe, magnified «0 diameters. 2. Seed-vessel of Fern, at the moment when the ring straightens itself. 3. Leaflet of Black Maiden-hair Spleen wort Fern.
4. Two sori, or collection of seed-vessels, of Spleenwort Fern, magd. 12 diams. 5. Sorus of
Hart's-tongue Fern, magd. 6 diams. 6 Part of a leaflet of Shield Fern. 7. Sorus, magd. 10 diams. 8. Sori of Polypody Fern, magd. 7 diams. 9. Sori and part of leaflet of Hare's-foot Fern, magd. 5 diams. 10. Thin section of Limestone, magd. 20 diams.
II . Group of twenty seed-vessels, natural size. 12. Group of twenty seed-vessels, magd. 6. diams.
13. Leaflet of Polypody. 14. part of a leaflet of Hare's-foot Fern.
Objects for the Microscope. 89
one of which crosses a small transverse vein between the Prcebrackial and Cubital, and the second, when present, runs behind the Pobrachial vein.
These examples of wings are most useful in awakening attention to the importance of minute observation, to the perfect order of Creation in all its parts, to the distinct individuality of each tiny fly in the presence of Him who made it. How little we think of this ; how carelessly we glance at the flies on our window-panes ; they are nearly all alike to our unseeing eyes. We complain of them, lay traps for them, kill them, but it seldom occurs to us that we had better study them.
WING OF MIDGE.
(PsycJwda.j
Only two examples more will I give— the wing of a Midge and the wing of a Gnat. These both belong to the first order of Diptera, the Tipulidse, which comprises all the Gnats, Midges, and Daddy-long-legs, or Tipulae. There are many more veins in this tiny wing than in any yet noticed, and the number of areolets or enclosed spaces in the wing is thirteen, every vein thickly covered with fine hairs ; these are supposed to assist the insect in its downward flight, by fixing the atmospheric fluid, which glides over it as they rise.
The motion of a little Midge on the window-pane is always zigzag, from right to left, and left to right. Some wings have six or seven spots upon them, and are called Psychoda sexpunctata.
WING OF GNAT.
This wing differs in the various species of Gnats which haunt our waterbutts, and tanks, and stagnant ponds. Some have more beautiful scales than others, but this wing of the common Gnat (Culex pipiens) is a good study and a most pleasing object. Look at it with the lowest power for the veining, and then with the highest for the scales.
The Gnats belong to that division of flies called Tipu- lidae, and also Nernocera, which means having the head
6
90 Objects for the Microscope.
branched. They all have long and beautiful antennae, which, in the males, are plumed and whorled like the stems of Equisetum.
The wings are narrow and lanceolate.
Sub-costal vein ends a little before the tip of the wing.
Radial, branched from the Sub-costal, and is forked.
Cubital vein begins from the Prcebrachial small transvese.
Mediastinal is between the Radial and Costal.
Prcebrachial is also forked. There are fourteen areolets.
The scales of a Gnat form test objects of the defining power of an object glass. Scales are composed of two or three layers of membrane, and probably the longitudinal ridges in these scales may represent folds of the outer membrane. We should not only see these striae, but the delicate transverse markings and projections of the lines beyond the top of the scale.
Gnats fly silently in winter and early spring, before the thirst for blood is awakened, and then the female only sounds the shrill clarion of war in her eager flight to and fro. See the Gnat (Culex), mounted whole, and for the complete knowledge of Flies, consult ' Walker's British Diptera,' vol. iii. ; ' The Insecta Britannica,'
WING OF COLEOPTERA.
Beetles have four wings ; but the upper pair, being crusta- ceous and used only as a protection for the under pair, are called Elytra. Their use is obvious from the habits of the Coleoptera ; tLey burrow in the ground and reside under the bark of trees, or beneath stones, when the undefended membranous wing would receive the greatest injury. The under wing is particularly described when examining the slide of Telephorus.
Both of these should be mounted and observed. The upper pair, or Elytra, if properly prepared, are very beau- tiful polariscope objects, especially those of Dytiscus and Cockchafer (Melolontha).
But there is a more important notice to be taken of the internal structure of the Elytron. Dr. Hicks discovered the same vesicles here as he did in the antennae of Flies
Objects for the Microscope. 91
and Bees. (See Antennae.) The wing-nerve branches over the Elytron, and those dots which exhibit the black cross with polarized light, are vesicles or organs of sensa- tion, to which a distinct branch of the nerve maybe traced.
Soak the Elytron in potash for a week or more, and when perfectly transparent mount in balsam.
The under wings exhibit groups of these vesicles on the under side of the sub-costal nerve, as many as 200 and 300 in each wing. Observe the wing of Strangalia, a Longi- corne Beetle. (See 'Journal of LinnaBan Society,' vol. i. p. 136, Nov. 1, 1856). See also Elytra of Diamond Beetle.
WING OP CRICKET.
(Acheta domestica.)
This is mounted to show the organ of sound, the drum and file by which the male Cricket chirps. Each of the upper wings, or Elytra, has a round transparent space called the drum, or tympanum ; at the base of each Elytron is a transverse horny ridge, furnished with numerous short transverse ridges or teeth, and forming a 'kind of bow or file. The insect rubs the Elytra across one another, and the grating of the files, together with the action of the drum as a sounding-board, causes the loud chirp. Some naturalists think that the legs work against this file and produce the sound, particularly in the Grasshopper, whose thighs are armed with rough ridges and short spines, and act as the bow against the files and drum of the Elytra.
The male Cricket only chirps. The female, silently at home, occupies herself in laying about 300 eggs and in rearing her brood. The tongue of a cricket is a beautiful object.
SCALES OF INSECTS.
The feathers of a Moth, a Butterfly, a Gnat, the scales of a Beetle, of a Weevil, of the Podura, are all both favourite and useful objects for the microscope. It is well known to every one that the dust which remains on our fingers after touching a butterfly's wing is a mass of beautiful feathers,
92 Objects for the Microscope.
or scales, varying in shape and colour with the species ; and that some are so delicately ornamented with a tracery that no unassisted eye can see that they form test objects for the defining power of the microscope.
Besides that use, we learn much from viewing a part of a butterfly's wing as an opaque, and observing how the scales are arranged on the membrane of the wing exactly like the tiles on the roof of a house ; — this is called being " imbricated "; each scale furnished with a point at one end which fits into a cup -like socket, attached to the skin of the body or the membrane of the wing. When the scales are rubbed off and transparent, we can better observe their structure, and we have some excellent examples in the slides numbered here.
SCALES OF MOEPHO MENELAUS.
Each scale or feather consists of three distinct laminae, two external and coloured, the inner one a highly polished colourless membrane, which reflects the light and increases the brilliancy of the scale. The Morpho menelaus, a large foreign butterfly of gorgeous blue, has striated scales, and with very high power, each line is slightly beaded, giving the appearance of transverse scoriae ; but to see this the achromatic condenser must be used.
SCALES OF POLYOMMATUS ARGUS,
a British Butterfly common as the pretty blue butterfly of the cornfield, or the seaside Downs ; has peculiar scales shaped like a battledore with long handle, and the longi- tudinal lines are swollen at intervals into rounded eleva- tions, which give it a dotted appearance, except towards the base, where a crescent-shaped cloud of minute pigment- cells crosses the scale, and forms a distinguishing mark of the species.
SCALES OF HIPPARCHIA JANIRA,
our little meadow brown Butterfly, which flits so merrily about the long grass in June to October, laying its exqui- site eggs upon the stems, from which a green striped caterpillar emerges in due time. These are the scales of
Objects for the Microscope. 93
its brown wings, most excellent test objects, and giving different markings. When dry, or in balsam, or when viewed by oblique or direct light, we see that the rounded end is toothed, and bears a brush-shaped appendage.
SCALES OF PONTIA BRASSICA.
The common Cabbage Butterfly, whose history is too well known to need remark ; the earliest and latest of our summer friends and garden enemies. There are several shapes in the scales of its wing, a very long and slender one, and some more of the battledore shape, and heart-shaped, with beautiful striae. Observe also a portion of the mem- brane, where the scales or feathers are rubbed oif. The apertures into which they are fixed are little cups or tubes, the orifices of which are set backward ; and around each are radiating folds of the upper membrane, giving them a star-like appearance.
SCALES OF THE SILKWORM MOTH.
The Silkworm Moth (Bombyx mori) has a variety of scales, toothed, and broad or narrow, and Leuwenhoeck reckoned no less than 400,000 of these delicate scales on the wings of one moth.
SCALES OF CLOTHES MOTH.
From the under side of that troublesome little Tinea we obtain a beautiful test object of very fine stria3. Also from the Podura.
SCALES OF PODURA.
The Podura is a small gray wingless insect with six legs, and a long forked tail, bent inwards, and by means of which it leaps and springs about in the sawdust of our cellars, and under stones, and in moss in damp places.
SCALES OF LEPISMA SACCHARINA.
A first cousin of Podura, haunting our sugar stores, and originally a native of America. It does not leap so well as Podura, if at all ; for its body does not terminate in a forked tail, but in several long thread-like styles, and it runs swiftly along, the little silvery gray body closely covered
94 Objects for the Microscope.
with these beautiful scales which require high and good powers to see distinctly.
A few words may be added on the appearance which Podura scales should present as a test object. Under a medium power they resemble watered silk ; light and dark lines wave across the scale in irregular bands ; but with better definition every dark band should be resolved into rows of short lines, thick at one end, and very fine at the other. Yet these apparent lines are not lines. We must have a higher power, a good quarter-inch lens, and then with careful management of light— always a most impor- tant thing — we shall see that the apparent lines are really spaces between the wedge-like particles which make up the layer or upper surface of the scale. As a test object it is out of fashion ; the dots of the Pleurosigma and the striae of Grammatophora and Pygidium of a flea being preferred by many scientific observers.
ELYTRON OF DIAMOND BEETLE.
A most beautiful object, to be looked at with reflected light — that is as an opaque. These brilliant spots are groups of scales, fashioned precisely like those of a butterfly's wing, but owing to their iridescence, to the peculiar thinness of the upper layer and the reflecting power of the secon- dary layer, the colour changes like that on a soap-bubble by the varied position of the light, the dark cell in which the scales are set adding to their brilliancy. The Diamond Beetle is one of the weevil tribe, and a native of South America; but we have smaller Diamond Beetles in our own country, and the Curculio of the oak and of the beech, a little green and gold weevil, by no means rare on nettle- plants, is quite as beautiful under the microscope, having the same kind of scales, set in dark cup-like recesses on its elytra.
FEET AND LEGS OF INSECTS. FOOT OF SYEPHUS.
Although the feet are better studied with the leg and upon the whole insect, yet as those specimens are not so
Objects for the Microscope. i)5
easily obtained as the foot of Syrphus, it should by all means form part of an educational box.
The Syrphus is one of those flies which vibrate over our flowers in the summer, and haunt the Michaelmas Daisy in the autumn. They are called Drone-flies and Wasp- flies, and are mistaken sometimes for one of the Hyme- noptera.
This foot displays that pair of membranous expansions called pulvUli which enable the fly to walk up and down smooth surfaces, on glass and on ceilings, in opposition to the laws of gravity. They are fringed with minute hairs, each of which is tubular, and secretes a viscid fluid which attaches the foot to the surface of the glass or wall, and the hooks on either side act as fulcra or props, with which the fly pushes against the substance when it desires to detach itself. The joints above the pulvilli are called tarsi.
LEG OF DYTISCUS, OR DYTICUS.
A most splendid object for the polariscope. The Dytiscus is a large water-beetle, common in ditches and ponds, and this is the fore-leg of the male. That large round disc is composed of three joints of the tarsi, which are studded with suckers ; one is extremely large, furnished with radi- ating fibres, and another is somewhat smaller, with single cup-like suckers raised on stalks, altogether giving it an immense power of adhesion.
FOOT OF WASP,
another favourite object for the polariscope: the tarsal joints are well seen, as also the hooks on each side of the pulvillus.
FOOT OF OPHION.
These toothed claws belong to an Ichneumon-fly (Ophion), which deposits its eggs in the larva or caterpillar of a moth (Bombyx Vinula, Puss Moth). The fly is yellow and has a sickle-shaped body, the ovipositor slightly exserted. — (See Hymenoptera Microgaster.)
96 Objects for the Microscope.
HIND-LEG OF BEE.
This is to show the peculiar structure of the hind-leg of the Hive-bee. The worker-bee— not the queen, nor yet the drone — has this beautiful contrivance for gathering the bee-bread, and carrying it home to the hive. The Bee collects the pollen of flowers, and rolls it into little pellets, which she places in two hollows on the outside of her hind- legs, called the baskets. This is done by her mouth and these hairy legs, which help to collect the pollen, and work it into shape and consistence.
Every leg has ten rows of these hairs, and sixteen hairs in a row. Count them, and observe how short and stiff they are, exactly what the Bee wants for her work.
FORE-LEG OF BEE.
The fore-legs of the Hive-bee, or Carder, or Humble-bee, exhibit a peculiar notch and spur on the tibia, which the insect uses for clinging each to the other in the festoons of wax-secreting labourers, or for nipping the legs of an enemy. There is a deep notch edged with stiff short bristles, and above it a spur, fashioned somewhat like the blade of a pocket-knife, which closes over it, and must be a most useful appendage to the busy Carder-bee in hackling its moss. It must not be soaked long in potash or the spur falls off. Mounted dry for the binocular it is well seen, and the modifications adapted to each species are very interesting.
LEG OF GYRINUS.
The Gyrinus is a small Water-beetle, that merry little fellow who assembles with a host of comrades, whirls round in ceaseless play on the surface of the quiet pond, or sunny margin of the river. Boys call it the Whirligig Beetle. These curious hind-legs, of which he has four, are the oars and helm by which he propels and steers his little body with such velocity through the water.
The structure is remarkable, the femur and tibia are somewhat triangular, the latter fringed with short spines, and long flattened filaments; in the middle pair of legs
Objects for the Microscope. 97
these filaments are on both margins, on the hindmost only on the outer margin.
The tarsi are five-jointed, but the three upper ones are most curiously fashioned into long leaf-like lobes, fringed with spines, the fourth joint is about the same size and semi-circular, and the fifth very short-armed, with two claws, as indeed is each tarsal joint.
Circulating currents may be seen in the hind-legs. Also, if you catch one, examine its very curious eyes divided into two parts, the upper group for viewing objects in the air, and the lower those in the water. The antennae are remark- able, not only in shape, but in being retractile and having each an ear-like joint fringed with colourless flat hairs, which shuts it into the cavity in front of the eyes.
LEG OF BRACHINUS.
(Bomladier Beetle.)
A small red and black Beetle, common near London, which has the power of defending itself by letting off smoke with the noise of a pop-gun. It is furnished with an internal bladder capable of firing off twenty shots in succession. If this smoke gets into the eyes it makes them smart as if they had been bathed with brandy. This little fellow has a bitter enemy in the Calamosa, a larger beetle, which hunts it without mercy. As it finds it impossible to escape by speed of foot, it stops short and awaits its pursuer ; but just as he is about to seize it, he is saluted by a discharge, and while he is for a moment stupefied with surprise, the bombadier endeavours to gain a hiding place. — (See l Insect Miscellanies'; also Bouche de Brachinus, in Baker's col- lection.)
LEG OF ANCHOMENUS,
a small green Beetle, nearly allied to Brachinus, as the leg will show ; both of them have that very curious curve in the tibia which is peculiar to the Carabici. These are swift-running beetles, and many of them have no wings under their elytra : they belong to the Pentamera, having five tarsi or ankle-joints. — (See also Bouche et Palpes, in Baker's collection.)
98 Objects for the Microscope.
LEG OF CALATHUS CASTELLOIDES.
A very abundant and pretty Beetle about half an 'inch long, black or brown, with black, or sometimes red legs. Found under stones near London. It has five joints in the tarsi, therefore belongs to the first order of Coleoptera, the Pentamera. The claws are toothed like a comb, and the male has three joints of the anterior tarsi dilated. (See also Bouche et Palpes de Calathus, in Baker's col- lection.)
STING OF WASP AND BEE.
The weapon of defence given to these insects consists of a barbed dart and a bag of subtle poison. The dart itself is composed of two blades, with serrated edges, enclosed in a sheath, and attached by strong muscles to the side of the abdomen ; near the slit by which it protrudes are two hairy appendages, which act as brushes and keep it clean, and at a short distance within a slender canal leads to the bag of poison, which, pressed by the muscles in the act of stinging, gives out the acrid drop which irritates the wound to such painful swelling.
STING OF GNAT.
See Head of Gnat.
STING OF TABANUS.
See Head of Tabanus.
EGG OF BOT-FLY, OR 03STRUS.
There is not a more curious and interesting object than this. Those little spots which cover the fore-legs of horses from the latter end of July to the end of September, are eggs like this, deposited by a fly called (Estrus, or Gad-fly. The longest period of this fly's life is passed in the intes- tines of the horse, and all the winter every horse exposed by field work or pasture feeding to the attacks of the (Estrus is full of the larva? which hatch from this egg.
The fly itself appears only in July, and is properly called
Objects for the Microscope. 99
Gasterophilus, or Stomach-lover. A tawny body very hairy, wings dingy white, and with a transverse gray band ; with- out any proboscis, for it lives but a very short time — only to lay its eggs and die. The abdomen is bent inwards, the female having a retractile tube consisting of four pieces, -and terminating in five points, within which she holds the egg, and hovers over the horse, lightly darting at him, and depositing each egg upon a hair. This egg is firmly attached by some glutinous substance, and is, as you may observe, finely striated and furnished with an operculum or lid, hinged and fitted on that oblique top. When the larva is fully formed, the egg, which is always placed where the horse most frequently licks itself, opens under the warm moisture of the tongue, and the larva, which is provided with hooks for the purpose, clings to the tongue, and is swallowed with the saliva or the food. By two long sharp hooks you may see folded downwards on the larva it attaches itself to the inner coat of the horse's stomach, nourished by the warmth and the mucus until the spring, when it has grown nearly an inch long ; it then unhooks itself, mingles with the food, and passes out as what grooms call hots. The next change is that it wriggles into the earth, and becomes a pupa, lies there a few weeks, and comes forth as SL perfect fly, to rise up and seek its mate, who dies imme- diately after their union, and the female lingers but a few- days longer, to deposit a hundred eggs, or more, as her appointed task on earth.
100 Objects for the Microscope.
CHAPTER III.
INSECTS MOUNTED WHOLE.
COLEOPTERA, HEMIPT. HYMENOPT., as C. iv. DIPTERA.
HITHERTO we have only examined parts of various insects, and whilst they have surprised and delighted us by their curious or beautiful forms, and shown us how perfectly they are adapted to the wants of each insect ; yet we have but a very imperfect idea of the anatomy of any single insect without one of these beautiful preparations.
They cost years of thought and experience to bring to this perfection. To preserve the delicate body entire, yet make it perfectly transparent, so as to display every joint, and in many cases its internal muscular structure ; to fix it in its natural position, and embalm it, as it were, in the clear preservative medium, Canada balsam ; to draw out the beautiful tongue, or the wonderful ovipositor, and show the varied and fragile antennae, or lay out the fine tissue of the wings, was the work of many a day before this art was attained.
And these slides are so valuable to the young student of natural history that no microscope box should be without one or two illustrations of each of these orders — Coleoptera, Hemiptera, Hymenoptera, and Diptera.
No engraving can teach the lesson upon insect anatomy so well as that which is learnt at the microscope with one of these slides upon the stage.
Take, for instance, one of the Coleoptera —
THE TELEPHORUS, OR SOLDIER-BEETLE.
We find this little creature abundantly in our gardens, on hedges, and on the long grass of a sunny June morning ; but especially on the flowers of all Umbelliferse, such as
Objects jor the Microscope. 101
the wild Parsnip, Carrot, and Parsley. They have orange- coloured elytra, or green or buff, tipped with red. Chil- dren call them " soldiers" and " sailors." Carnivorous in their tastes, they haunt flowers for the smaller insects they feed upon, and seize them fiercely in their strong pointed mandibles. When we touch them they depress their heads, become motionless, and counterfeit death.
They lay their eggs in damp shady places in the earth, where the larvae hatch and live. These are velvety, black, long, soft-bodied maggots, with strong mandibles on their heads, and a curious neshy tubercle beneath the last segment of the body, which they use in walking.
Use your lowest power in examining these preparations for a general view of the insect, and then change the object glass progressively upward to the highest power for such parts as require particular attention — the tongue, the eye, &c.
The first part to look at in a slide of Coleoptera is the foot, because the number of joints immediately above the claw, which are called tarsi, determines its position in the family group. All the Beetle tribe are divided into families according to the number of joints of their tarsi. There are four sections —
The Pentamera . or five-jointed. The Heteromera . or five-jointed anterior, and four- jointed posterior tarsi.
The Tetramera . or four joints to all the tarsi. The Trimera . . or three-jointed tarsi.
The foot of Telephorus, having five joints, belongs to the first section. Observe how deeply the penultimate joint is bilobed — that the tibia or joint above the tarsi has two small spurs — that the femur or thigh is stout, and attached to the thorax by two other joints called the coxa and the trochanter.
Next observe the antennae ; for after deciding this little beetle to belong to the section of the Pentamera, you will know that it is also one of the Serricornes, or third family
102 Objects for the Microscope.
of the Pentamera, by its long slender eleven-jointed antennse of the same thickness throughout.
Next examine the curious hatchet-shaped joint at the end of the palpi — small feelers attached to the jaws, and which are very important points for observation, as their number and shape determine the species of many beetles.
We now see the various parts of the mouth — the labrum or lip notched in front ; the two hairy maxillce formed of five pieces delicately fringed, and used for cleansing the food ; two strong mandibles or jaws for seizing their prey.
Two compound eyes which, in the male, occupy nearly the whole of the head.
The thorax, or body, to which are attached the three pairs of legs, and the wings and wing-cases.
This thorax is a wonderful piece of mechanism. It cannot be so well seen in this slide, because the elytra or wing-cases partly cover it ; but it should be carefully studied in various specimens. There are three chief parts —
The pro-thorax ; the segment nearest the heart, and supporting the first pair of legs.
The meso-thorax : bearing the elytra, or wing-cases, and the middle pair of legs.
The meta-thorax ; bearing the wings and the last pair of legs.
But these are again composed of no less than twenty- two smaller pieces, equally distinct and present in the thorax of the tiniest beetle ; and if we consider the complicated machinery necessary for the direction and control of all the muscles required for insect locomotion, the care bestowed upon the formation of the thorax will be at once accounted for. The movement of the legs in running, creeping, climbing, swimming, fighting, seizing their prey, cleansing their bodies, and the varied motions of the wings and wing-cases — these all demand distinct muscles and points of attachment. The whole cavity of the thorax is occupied by the wing and leg muscles, and the great ganglion of nerve which directs them as a viceregent from the seat of sensation, the head.
Objects for the Microscope. 103
And whilst looking at the thorax of this little Beetle, as hereafter we may look at that of a Fly, it will not lessen pur pleasure to be reminded of the many kinds of muscles that worked unerringly the will of this small creature. It had its levator muscles for raising its limbs ; depressors, antagonistic to these, for depressing them ; flexors for bend- ing the joints ; extensors for unbending or extending them ; abductors for drawing an organ backward, and abductors for drawing it forward ; constrictors that contract a body or an opening as in breathing; laxators that relax it. All these are in quick action in the little insect that runs over your hand or escapes from your eye ; all these have been planned and attached, and the numbers so accurately inter- woven, that they work without hindrance or confusion by the creative word of the Most High.
As the head for sensation, with its ganglion and branch- ing nerves, and the thorax for locomotion, so the abdomen, usually in nine segments, is appointed as the digester of food and the organ of generation.
The internal parts of an insect cannot be seen in these preparations. We must therefore confine our attention to the external anatomy, and, before this slide is put away, examine the wing.
The wing of a Beetle should be compared with that of a Fly, in order to appreciate its peculiar structure. The substance is membranous, double and joined together by canals or nervures, through which the blood circulates — a tracheal vessel runs, and a nerve, branching from the thoracic ganglion, and giving off innumerable fibres to groups of vesicles situated immediately beneath the costal nerve. This is only seen with very high powers and good glasses ; also requiring a particular preparation of the wing. It must simply be soaked in turpentine for a week or more, and mounted in balsam warmed just enough to receive the wing, when the tracheal vessel, the nerve, and the vesicles, may be distinctly seen with a good £-in. or J-in. object glass.
That strong nerve on the forepart of the wing is the costal nerve. As the Beetle's wing is folded under the
104 Objects for the Microscope.
elytron when in repose, the costal nerve ends abruptly, as we see, at about half the length of the wing, and turning backward into the post-costal nervure, forms a kind of hook, strengthens the base, and allows of the easy folding up of the tip of the wing.
There is a particular provision made for the regulation of the specific weight of the beetle's wing by means of a long pocket just under the costal and mediastinal nervures, called the Phialum, into which a liquid is introduced at the will of the insect, which augments its powers of resistance in flight.
The veins, or nervures, are so placed throughout this wing as to strengthen and stretch every part : at the same time to admit of its being closely and easily folded under the protecting elytron ; a most necessary arrangement for creatures who live in the earth or under stones, or in the water, where the delicate texture of the wing would be in constant danger of destruction.
Having thus examined one specimen of the Beetle tribe, we shall be able with increased interest to look at another, one of the small Water-beetles.
HELOPHORUS GRANULARIS.
This is an abundant little creature in our ponds and ditches, feeding on decayed or vegetable matter, and, being easily procured, is selected as an example of a Pentamerous Coleoptera, but of the family of the Palpicornes, the antennae being very different from those of the Telephorus. These are clubbed, composed of nine joints, and carried backwards.
It is a bad swimmer, and the legs are scarcely, if at all, feathered ; the striped pro-thorax and the beautifully dotted elytra make it a favourite and valuable object.
The sculpture of the elytra of Beetles is most remark- able ; the ridges strengthen, the furrows lighten, the dots give air to the spiracles beneath. In the Helophorus alternate rows of large and small dots answer both pur- poses, and usefulness as well as beauty write the wisdom of God upon the wing-case of this little creature.
Objects for the Microscope. 105
CATHEKETES URTIC^.
This is a lovely little Beetle ; as we see by its tarsi, it is one of the Pentamera, though at first sight easily mis- taken for one of the four-jointed Coleoptera, as the fifth joint is very small, and only visible from beneath. The antennae show that it belongs to the Glavicorne family, for they are clubbed. This particular little Beetle is one of a flower-loving group called Nitidulidce, always easily recog- nised by having eleven joints in the antennae, and the last three in a club, or strung like beads, with an interval between each. The spotted elytra are beautiful. The facetted eyes and the delicate mouth will require a higher power rightly to examine them. And this exquisite insect is one we may see in swarms upon nettles revelling in the pendent blossoms any sunny summer's day — very small black creeping things we pass unheeded by.
COCCINELLA, OR LADY-BIRD.
This familiar little visitor is not only a beautiful object for the microscope, but a real friend to the florist, who is apt to be disappointed and angered by what is called the " green blight " upon the roses, and is not perhaps aware that two or three Lady-birds would clear it all away much better than the usual means applied by gardeners.
The Lady-bird is particularly fond of Aphides, and, in its larva state, pupa state, and perfect form, will greedily levour them, darting at an Aphis, and seizing it in those strong little jaws, shaking it as a terrier does a rat, and sucking its life away ; then dropping the empty body, and springing upon another and another. The little Coccinella cias frequently saved our fir plantations from the host of lestroying Aphis in the spring ; and our bean-fields, when attacked by the black blight (Aphis faboa), are often cleared again in an incredibly short time by the avenger G-od has given us in this lovely little Beetle.
It is one of the Trimera, three joints only in the tarsi.
7
106 Objects for the Microscope.
The antennae eleven-jointed, and terminated by a reversed conical club.
I must not describe so fully any more of these beautiful slides; but recommend you, if possible, to obtain the following whole mounted Coleoptera:
Lcecophilus Minutas, remarkable for its feathered legs.
Hattica, or Turnip-fly, „ „ thick muscular
thighs for leaping.
Thyanus, or Grass-flea, also with muscular thighs and sculptured elytra.
Dimonia cynoglossi . one of the Tetramera, with thick- ened thighs and beautiful head.
Haliplus confirms . one of the Hydrocantheri, or Swimmers, with beautifully fringed legs for swimming.
Hypliidius ovatus . one of the Water-beetles, with fringed legs for swimming, and a curious spine at the tip of each elytron.
Oyrinus natator . a Water-beetle. (This is described in leg of Gyrinus.)
HEMIPTEBA.
These are sucking insects. Their mouth has a long retractile tube, and several flne lancets, forming a long pro- boscis, which is laid along the breast during repose, and maybe seen in all the Field-bugs (Cimex) and the Aphides, which belong to this order. The wings are membranous, and covered with semi-transparent cases analogous to the elytra of Beetles. The tarsi are always three-jointed. A few of them inhabit the water, and of these the Velia rivu- lorum and Notonecta are mounted whole.
VELIA RIVULORUM.
Most people have observed groups of water insects sporting on the surface of small ponds, or swimming
Objects for the Microscope. 107
against small streams, walking lightly on the still water, and resting on the stems of grass or water weeds around. One species (Gerris) has a long thin black body and very long legs ; but Velia may be known by its scarlet spots on each side of its body. The two-jointed sucker and the wing-cases should be carefully examined.
NOTONECTA, OR THE WATER-BOATMAN,
is a beautiful preparation, exhibiting the retractile sucker, which is a formidable weapon, and pricks sharply; the eyes very large ; the hind-legs fringed with long hairs and in the form of oars, which it uses with great rapidity, rowing or swimming always on the back, and looking like a canoe propelled by a clever boatman. The eggs of this insect are found abundantly on the other side of Water- lily leaves, or of Potomageton ; small flask-like eggs through which, in an advanced state, the red eyes of the little Notonecta may be seen, and when it comes forth, it only resembles its parent in its feathered legs and quick movements, having no wings until it has moulted several times, and changed from the larva to the pupa state, in which, however, it is by no means inactive, for the pupa of Hemiptera feeds as heartily as the perfect insect. This Notonecta is a fierce and powerful enemy to all smaller aquatic insects, transfixing them with his sharp proboscis, and sucking their life away.
REDUYIUS, OR BED-BUG,
is one of this order, and the sucker, though short, is very strong, and capable of producing much pain.
CIMEX, OR FIELD-BUG.
These are beautiful objects when mounted. The head is prolonged like a snout, more or less triangular ; and the sheath of the sucker is composed of four distinct joints ; they prey upon other insects ; the body is often brightly coloured and spotted. We find them abundantly on long grass or field flowers in the hot days of summer, and one
108 Objects for the Microscope.
species, Pentatoma griseus, is interesting from the care which the female takes of her young, not only in brooding over her eggs, but in leading her little family about as a hen does her chickens.
APHTS.
A specimen of the green or black blight will be very interesting to the florist, although the Aphis of the elder or the box are prettier in having variegated bodies. There are no less than 160 known species, and few insects have a more curious and interesting biography. 'Kirby and Spence's Entomology/ and THistoire des Hemipteres, de MM. Serville and Amyot,' will give abundant information to the student of natural history.
I can only draw attention to the external form, and point out the remarkable long antennae thrown backwards ; the proboscis, fine and sharp, with which it pierces the young shoots of our rose-trees, or the fibres on the under side of our currant-trees and vines, causing them to curl up and turn red. Those two horns on the back are tubes from which exude small drops of saccharine matter or honey- dew, of which the ants are so fond that, wherever these Aphides abound, there the Garden Ant will follow, and may be seen sucking it from them.
These Ants take absolute possession of some species.
The Aphis radicum, which feed on the roots of plants, are kept by the Yellow Ants in their formicaries under-ground, and milked as cows are by us. This may be watched on rose-trees or oak-trees, the little Ants following an Aphis, tapping them, and pressing their sides to make them jerk out the sweet fluid.
The tarsi are only two-jointed, the eyes compound. They are both winged and wingless, and the Aphis wings are always carried with the fan edges upward, and have either a row of booklets or a tuft of seven or eight hooks, which attach the wing-case and wing together, like the hamuli of the Hymenoptera.
The rapid increase of these insects is astonishing : a single Aphis may in one season become the parent of as
Object* for the Microscope. 109
many as 5,904,900,000 descendants. The fact that these are produced by females without more than one impregna- tion throughout nine generations long perplexed our natu- ralists. Bonnet isolated females most carefully, and obtained nine generations in three months. It is now ascertained that certain females couple and lay eggs only in the autumn, and that throughout spring and summer the young ones are produced alive by a process of gemmation from what are called Nurses.
All through the winter one solitary female Aphis, which I had placed in my bedroom window on the leaf of a tulip, continued to present tne with pretty little pink-eyed stag- gering things, until the whole plant was covered with them ; and very curious it was to see the small Aphis keep close to its mother's side for some hours, whilst she seemed tenderly to caress it with her long antennae, until another required her care, and this one was able to join the group of sisters at a little distance, whose tiny suckers were plunged into the juices of my Van Tromp.
For an account of their enemies and our avengers, see Hymenoptera, Aphidius avena.
APHROPHORA, OR CUCKOO-SPIT.
I suppose all florists will like to have this slide, because they so well know a certain frothy substance which abounds on their Carnation plants, Lychnis, Rose-trees, and Willows, in which sits a little green creature with red eyes ; a soft, frightened, innocent-looking little larva, which I never could help covering again with the white froth if I had blown it aside for a moment. And this was the defence of the young Aphrophora we are now looking at : it passed from that larva into a pupa, and then into this perfect state with wings and wing-cases, with a long sucking tube, which pierced the stems of our flowers and dried up the plant by abstracting the sweet fluids needful to its growth. Observe the mottled wing-case, all of uniform texture, which shows it to belong to the second division of Hemiptera, called Homoptera ; the wing with longitudinal nerves forked at the tip. The legs, which leap wonderfully high, are remarkably circled at each
110 Objects for the Microscope.
tibia by a crown of spines. The mouth is better displayed in a specimen of Cimex.
THRIPS.
This is not now one of the Hemiptera, but belongs to a very small order called Thysanoptera. We find these very minute insects swarming in our flowers, especially in the Carnations and Lilies. They are