Antennæ, their Structure and Use--Eyes, Compound and
Simple--Breathing Organs--Jaws and their Appendages--Legs, Feet,
and Suckers--Digestive Organs--Wings, Scales, and Hairs--Eggs
of Insects--Hair, Wool, Linen, Silk, and Cotton--Scales of
Fish--Feathers--Skin and its Structure--Epithelium--Nails, Bone, and
Teeth--Blood Corpuscles and Circulation--Elastic Tissues--Muscle and
Nerve.
We now take leave of the vegetables for a time, and turn our attention
to the animal kingdom.
On Plate VI. may be seen many beautiful examples of animal structures,
most of them being taken from the insect tribes. We will begin with the
antennæ, or horns, as they are popularly termed, of the insect.
The forms of these organs are as varied as those of the insects to
which they belong, and they are so well defined that a single antenna
will, in almost every instance, enable a good entomologist to designate
the genus to which the insect belonged. The functions of the antennæ
are not satisfactorily ascertained. They are certainly often used as
organs of speech, as may be seen when two ants meet each other, cross
their antennæ, and then start off simultaneously to some task which is
too much for a single ant. This pretty scene may be witnessed on any
fine day in a wood, and a very animated series of conversations may
readily be elicited by laying a stick across their paths, or putting a
dead mouse or large insect in their way.
I once saw a very curious scene of this kind take place at an ant’s
nest near Hastings. A great daddy long-legs had, unfortunately for
itself, settled on the nest, and was immediately “pinned” by an ant or
two at each leg, so effectually that all its struggles availed nothing.
Help was, however, needed, and away ran four or five ants in different
directions, intercepting every comrade they met, and by a touch of the
antennæ sending them off in the proper direction. A large number of the
wise insects soon crowded round the poor victim, whose fate was rapidly
sealed. Every ant took its proper place, just like a gang of labourers
under the orders of their foreman; and by dint of pushing and pulling,
the long-legged insect was dragged to one of the entrances of the nest,
and speedily disappeared.
Many of the ichneumon-flies may also be seen quivering their antennæ
with eager zeal, and evidently using them as feelers, to ascertain the
presence of the insect in which they intend to lay their eggs; and many
other similar instances will be familiar to anyone who has been in the
habit of watching insects and their ways.
It is, however, most likely that the antennæ serve other purposes than
that which has just been mentioned, and many entomologists are of
opinion that they serve as organs of hearing.
Fig. 15, Plate VI., represents a part of one of the joints belonging to
the antennæ of the common house-fly; it is seen to be covered with a
multitude of little depressions, some being small, and others very much
larger. A section of the same antenna, but on a larger scale, is shown
by Fig. 16, in order to exhibit the real form of these depressions.
Nerves have been traced to these curious cavities, which evidently
serve some very useful purpose, some authors thinking them to belong to
the sense of smell, and others to that of hearing. Perhaps they may be
the avenues of some sensation not possessed by the human race, and of
which we are therefore ignorant. Fig. 17 represents a section of the
antennæ of an ichneumon-fly, to show the structure of these organs of
sense.
We will now glance cursorily at the forms of antennæ which are depicted
in the Plate.
Fig. 1 is the antenna of the common cricket, which consists of a vast
number of little joints, each a trifle smaller than the preceding one,
the whole forming a long, thread-like organ. Fig. 2 is taken from the
grasshopper, and shows that the joints are larger in the middle than at
either end.
Figs. 3 and 5 are from two minute species of cocktailed beetles
(_Staphylínidæ_), which swarm throughout the summer months, and even in
the winter may be found in profusion under stones and moss. The insect
from which Fig. 5 was taken is so small that it is almost invisible
to the naked eye, and was captured on the wing by waving a sheet of
gummed paper under the shade of a tree. These are the tiresome little
insects that so often get into the eye in the summer, and cause such
pain and inconvenience until they are removed.
Fig. 4 shows the antenna of the tortoise beetle (_Cássida_), so common
on many leaves, and remarkable for its likeness to the reptile from
which it derives its popular name. Fig. 3 is from one of the weevils,
and shows the extremely long basal joint of the antennæ of these
beetles, as well as the clubbed extremity. Fig. 7 is the beautifully
notched antenna of the cardinal beetle (_Pyrochróa_), and Fig. 11 is
the fan-like one of the common cockchafer. This specimen is taken from
a male insect, and the reader will find his trouble repaid on mounting
one of these antennæ as a permanent object.
Fig. 12 is an antenna from one of the common ground beetles (_Cárabus_)
looking like a string of elongated pears, from the form of the joints.
The reader will see that in beetles he is sure to find eleven joints in
the antennæ.
Fig. 10 is the entire antenna of a fly (_Syrphus_), one of those pretty
flies which may be seen hovering over one spot for a minute, and then
darting off like lightning to hang over another. The large joint is the
one on which are found those curious depressions that have already been
mentioned. Fig. 8 is one of the antennæ of a tortoise-shell butterfly
(_Vanessa_), showing the slender, knobbed form which butterfly
antennæ assume; and Figs. 13 and 14 are specimens of moths’ antennæ,
showing how they always terminate in a point. Fig. 13 is the beautiful
feathery antenna of the ermine moth (_Spilosóma_); and Fig. 14 is the
toothed one of the tiger moth (_Arctia caja_). In all these feathered
and toothed antennæ of moths, the male insects have them much more
developed than the female, probably for the purpose of enabling them
to detect the presence of their mates, a property which some possess
in wonderful perfection. The male oak-egger moth, for example, can be
obtained in any number by putting a female into a box with a perforated
lid, placing the box in a room, and opening the window. In the course
of the evening seven or eight males are seen to make their appearance,
and they are so anxious to get at their intended mate that they will
suffer themselves to be taken by hand.
Fig. 9 is an antenna of the male gnat, a most beautiful object,
remarkable for the delicate transparency of the joints, and the
exquisitely fine feathering with which they are adorned.
We now arrive at the eyes of the insects, all of which are very
beautiful, and many singularly full of interest.
In the centre of Plate VI. may be seen the front view of the head
of a bee, showing both kinds of eyes, three simple eyes arranged
triangularly in the centre, and two large masses, compound eyes, at the
sides.
The simple eyes, termed “ocelli,” are from one to three in number, and
usually arranged in a triangular form between the two compound eyes.
Externally they look merely like shining rounded projections, and can
be seen to great advantage in the dragon-flies. The compound eyes may
be considered as aggregations of simple eyes, set closely together,
and each assuming a more or less perfect six-sided form. Their number
varies very greatly; in some insects, such as the common fly, there are
about four thousand of these simple eyes in one compound one, in the
ant only fifty, in the dragon-fly about twelve thousand, and in one of
the beetles more than twenty-five thousand.
Fig. 18 shows a portion of the compound eye of the Atalanta butterfly,
and Fig. 20 the same organ of the death’s-head moth. A number of
the protecting hairs may be seen still adhering to the eye of the
butterfly. Fig. 22 is a remarkably good specimen of the eye of a fly
(_Helióphilus_), showing the facets, nearly square, the tubes to
which they are attached, and portions of the optic nerves. Fig. 23
is part of the compound eye of a lobster, showing the facets quite
square. All these drawings were taken by the camera lucida from my own
preparations, so that I can answer for their authenticity.
On Plate VIII. Figs. 6 and 12, the reader will find two more examples
of eyes, these being taken from the spiders. Fig. 6 is an example of
the eight eyes of the well-known zebra spider, so common on our garden
walls and similar situations, hunting incessantly after flies and other
prey, and capturing them by a sudden pounce. The eyes are like the
ocelli of insects, and are simple in their construction. The number,
arrangement, and situation of the eyes is extremely varied in spiders,
and serves as one of the readiest modes of distinguishing the species.
Fig. 12, Plate VIII., represents one of the curious eyes of the common
harvest spider, perched on a prominence or “watch-tower” (as it has
been aptly named), for the purpose of enabling the creature to take a
more comprehensive view of surrounding objects.
* * * * *
Returning to Plate VI., in Fig. 21 we see a curiously branched
appearance, something like the hollow root of a tree, and covered with
delicate spiral markings. This is part of the breathing apparatus of
the silkworm, extracted and prepared by myself for the purpose of
showing the manner in which the tubes branch off from the “spiracle”
or external breathing-hole, a row of which may be seen along the
sides of insects, together with the beautiful spiral filament which
is wound round each tube for the purpose of strengthening it. One of
these spiracles may be seen in the neck of the gnat (Fig. 27). Another
spiracle, more enlarged, may be seen on Plate VII. Fig. 34, taken from
the wireworm, _i.e._ the larva of the skipjack beetle (_Eláter_), to
show the apparatus for excluding dust and admitting air. The object of
the spiral coil is very evident, for as these breathing-tubes extend
throughout the whole body and limbs, they would fail to perform their
office when the limbs were bent, unless for some especial provision.
This is achieved by the winding of a very strong but slender filament
between the membranes of which the tube is composed, so that it always
remains open for the passage of air throughout all the bends to which
it may be subjected. Flexible tubes for gas and similar purposes are
made after the same fashion, spiral metal wire being coiled within
the india-rubber pipe. A little piece of this thread is seen unwound
at the end of a small branch towards the top, and this thread is so
strong that it retains its elasticity when pulled away from the tube,
and springs back into its spiral form. I have succeeded in unwinding
a considerable length of this filament from the breathing-tube of a
humble bee.
Fig. 28 represents the two curious tubercles upon the hinder quarters
of the common green-blight, or Aphis, so very common on our garden
plants, as well as on many trees and other vegetables. From the tips of
these tubercles exudes a sweet colourless fluid, which, after it has
fallen upon the leaves, is popularly known by the name of honey-dew.
Ants are very fond of this substance, and are in the habit of haunting
the trees upon which the aphides live, for the purpose of sucking the
honey-dew as it exudes from their bodies. A drop of this liquid may be
seen on the extremity of the lower tubercle.
The head of the same insect may be seen in Fig. 24, where the reader
may observe the bright scarlet eye, and the long beak with which the
aphis punctures the leaves and sucks the sap. Fig. 29 is the head of
the sheep-tick, exhibiting the organ by which it pierces the skin of
the creature on which it lives. Fig. 25 is the head of another curious
parasite found upon the tortoise, and remarkable for the powerful
hooked apparatus which projects in front of the head.
Turning to Plate VII. Fig. 4, we find the head of a ground beetle
(_Cárabus_), valuable as exhibiting the whole of the organs of the head
and mouth.
Immediately above the compound eyes are seen the roots of the antennæ,
those organs themselves being cut away. Above there are two pairs of
similarly constructed organs termed the “maxillary palpi,” because
they belong to the lesser jaws or maxillæ, seen just within the pair
of great curved jaws called the mandibles, which are extended in so
threatening a manner. The “labial palpi,” so called because they
belong to the “labium,” or under lip, are seen just within the others;
the tongue is seen between the maxillæ, and the chin or “mentum”
forms a defence for the base of the maxillæ and the palpi. A careful
examination of a beetle’s mouth with the aid of a pocket lens is very
instructive as well as interesting.
Fig. 1 on the same Plate shows the jaws of the hive bee, where the same
organs are seen modified into many curious shapes. In the centre may be
seen the tongue, elongated into a flexible and hair-covered instrument,
used for licking the honey from the interior of flowers. At each side
of the tongue are the labial palpi, having their outermost joints very
small, and the others extremely large, the latter acting as a kind
of sheath for the tongue. Outside the labial palpi are the maxillæ,
separated in the specimen, but capable of being laid closely upon each
other, and outside all are the mandibles.
VI.
FIG.
1. Antenna, Cricket
2. Do. Grasshopper
3. Do. Staphylinus
4. Do. Cassida
5. Do. Staphylinus
6. Do. Weevil
7. Do. Pyrochroa
8. Do. Butterfly, Tortoiseshell
9. Do. Gnat, male
10. Do. Syrphus
11. Do. Cockchafer, male
12. Do. Ground Beetle
13. Do. Ermine Moth
14. Do. Tiger Moth
15. Do. Blowfly
16. Do. do. section
17. Do. Ichneumon
18. Eye of Butterfly, Atalanta
19. Eyes, Bee
20. Eye, Death’s Head Moth
21. Breathing-tube, Silkworm
22. Eye, Heliophilus
23. Do. Lobster
24. Do. Aphis of Geranium
25. Head, Parasite of Tortoise
26. Hind leg, Aphis of Geranium
27. Head, Gnat
28. “Paps” of Aphis
29. Head, Sheep-tick
30. Foot, Tipula
[Illustration: VI.]
The curiously elongated head of the scorpion-fly (_Panorpa_), seen
at Fig. 7, affords another example of the remarkable manner in which
these organs are developed in different insects. Another elongated
head, belonging to the daddy long-legs, is seen in Plate VI. Fig. 27,
and well shows the compound eyes, the antennæ, and the palpi. Fig. 2
represents the coiled tongue of the Atalanta butterfly; it is composed
of the maxillæ, very greatly developed, and appearing as if each
had originally been flat, and then rolled up so as to make about
three-fourths of a tube. A number of projections are seen towards the
tip, and one of these little bodies is shown on a larger scale at
Fig. 3. These curious organs have probably some connection with the
sense of taste. Along the edges of the semi-tubes are arranged a number
of very tiny hooks, by means of which the insect can unite the edges at
will.
Fig. 11, in the centre of the Plate, shows one of the most curious
examples of insect structure, the proboscis or trunk of the common
bluebottle-fly. The maxillary palpi covered with bristles are seen
projecting at each side, and upon the centre are three lancet-like
appendages, two small and one large, which are used for perforating
various substances on which the insect feeds. The great double disc
at the end is composed of the lower lip greatly developed, and is
filled with a most complex arrangement of sucking-tubes, in order to
enable it to fulfil its proper functions. The numerous tubes which
radiate towards the circumference are strengthened by a vast number
of partial rings of strong filamentary substance, like that which we
have already seen in the breathing-tube of the silkworm. Some of these
partial rings are seen on Fig. 12, a little above. The mode in which
the horny matter composing the rings is arranged upon the tubes is most
wonderful, and requires a tolerably high power to show it. The fine
hairs upon the proboscis itself afford most admirable practice for the
young microscopist. They should, when properly lighted and focused, be
quite black and sharp. Any errors of manipulation will cause them to be
“fuzzy.”
Fig. 5 shows the tongue of the common cricket, a most elegantly formed
organ, having a number of radiating bands covered with zigzag lines,
due to the triangular plates of strengthening substance with which they
are furnished, instead of the rings. A portion more highly magnified
is shown at Fig. 6, exhibiting the manner in which the branches are
arranged.
* * * * *
The legs of insects now claim our attention.
Fig. 9, Plate VII., shows the “pro-leg” of a caterpillar. The pro-legs
are situated on the hinder parts of the caterpillar, and, being set in
pairs, take a wonderfully firm hold of a branch or twig by pressure
toward each other. Around the pro-legs are arranged a series of sharp
hooks, set with their points inwards, for greater power in holding.
Fig. 10 represents one of the hooks more magnified.
Fig. 15 is the lower portion of the many-jointed legs of the
long-legged spider (_Phalángium_), the whole structure looking very
like the antenna of the cricket. Fig. 17 is the leg of the glow-worm,
showing the single claw with which it is armed. Fig. 26 shows the foot
of the flea, furnished with two simple claws. Fig. 16 is the foot of
the Trombídium, a genus of parasitic creatures, to which the well-known
harvest-bug belongs. Fig. 26, Plate VI., shows the leg of the green
Aphis of the geranium, exhibiting the double claw, and the pad or
cushion, which probably serves the same purpose as the pads found upon
the feet of many other insects. Fig. 8 is the lower portion of the leg
of the ant, showing the two claws and the curious pad in the centre,
by means of which the insect is able to walk upon slippery surfaces.
The Típula has a foot also furnished with a single pad (see Plate VI.
Fig. 30). This organ is seen under a very high power to be covered with
long hair-like appendages, each having a little disc at the end, and
probably secreting some glutinous fluid which will enable the creature
to hold on to perpendicular and smooth surfaces. Many of my readers
will doubtless have noticed the common fly, towards the end of autumn,
walking stiffly upon the walls, and evidently detaching each foot with
great difficulty, age and infirmity having made the insect unable to
lift its feet with the requisite force.
Fig. 21 is the foot of one of the ichneumon-flies (_Ophíon_), the
hairy fringe being apparently for the purpose of enabling it to hold
firmly to the caterpillar in which it is depositing its eggs, and
which wriggles so violently under the infliction that it would soon
throw its tormentor had not some special means been provided for the
purpose of enabling the latter to keep its hold. Fig. 20 is a beautiful
example of a padded foot, taken from the little red parasitic creature
so plentifully found upon the dor or dung beetle (_Geotrúpes_), and of
which the afflicted insect is said to rid itself by lying on its back
near an ant’s nest, and waiting until the ants carry off its tormentors.
Fig. 18 is the foot of the common yellow dung-fly (plentiful in pasture
lands), having two claws and two pads; and Fig. 19 shows the three pads
and two claws found in the foot of the hornet-fly (_Ásilus_).
Few microscopic objects call forth such general and deserved admiration
as the fore-foot of the male water-beetle (_Dytiscus_), when properly
prepared and mounted, for which see Fig. 13.
On examining this preparation under the microscope, it is seen that
three of the joints are greatly expanded, and that the whole of their
under surface is covered profusely with certain wonderful projections,
which are known to act as suckers. One of them is exceedingly large,
and occupies a very considerable space, its hairs radiating like the
rays of the heraldic sun. Another is also large, but scarcely half
the diameter of the former, and the remainder are small, and mounted
on the extremities of delicate foot-stalks, looking something like
wide-mouthed trumpets. In the specimen from which the drawing was taken
the smaller suckers are well shown, as they protrude from the margin of
the foot.
One of the larger suckers is seen more magnified on Fig. 14.
Plate VIII. Fig. 1, exemplifies the manner in which the muscles of
insects do their work, being well attached in the limbs to the central
tendon, and pulling “with a will” in one direction, thus giving very
great strength. This leg is taken from the water boatman (_Notonecta_),
and has been mounted in Canada balsam.
On Plate VII. Fig. 29, may be seen a curiously formed creature. This
is the larva of the tortoise beetle (_Cássida_), the skin having been
flattened and mounted in Canada balsam. The spiracles are visible
along the sides, and at the end is seen a dark fork-like structure.
This is one of the peculiarities of this creature, and is employed for
the purpose of carrying the refuse of its food, which is always piled
upon its back, and retained in its place by the forked spines, aided
probably by the numerous smaller spines that project from the side.
Fig. 33 shows part of the stomach and gastric teeth of the grasshopper.
This structure may be seen to perfection in the “gizzard,” as it is
called, of the great green locust of England (_Ácrida viridíssima_).
The organ looks like a sudden swelling of the œsophagus, and when slit
longitudinally under water, the teeth may be seen in rows set side by
side, and evidently having a great grinding power. The common house
cricket has a similar organ of remarkable beauty. Just above (Fig. 27)
is the corresponding structure in the hive bee, three of the teeth
being shown separately at Fig. 28.
* * * * *
We now cast a rapid glance at the wings of insects.
They have no analogy, except in their use, with the wings of birds, as
they are not modifications of existing limbs, but entirely separate
organs. They consist of two membranes united at their edges, and
traversed and supported by sundry hollow branches or “nervures,” which
admit air, and serve as useful guides to entomologists for separating
the insects into their genera. Indeed, the general character of the
wings has long been employed as the means of dividing the insect race
into their different orders, as may be seen in any work on entomology.
The typical number of wings is four, but it often happens that two are
almost wholly absent, or that the uppermost pair are thickened into a
shelly kind of substance which renders them useless for flight; while
in many insects, such as the ground beetles and others, the upper wings
become hardened into firm coverings for the body, and the lower pair
are shrivelled and useless.
Fig. 22 shows two of the wings of a humble bee, together with their
nervures, and the peculiar system by which the upper and lower pair are
united together at the will of the insect. At the upper edge of the
lower wing, and nearly at its extremity, may be seen a row of very tiny
hooks, shown on a larger scale at Fig. 25. These hooklets hitch into
the strengthened membrane of the upper wing, which is seen immediately
above them, and so conjoin the two together. The curious wing-hooks of
the Aphis may be seen on Fig. 24, very highly magnified.
Fig. 31 is the wing of the midge (_Psychóda_), that odd little insect
which is seen hopping and popping about on the windows of outhouses
and similar localities, and is so hard to catch. The whole wing is
plentifully covered with elongated scales, and is a most lovely object
under any power of the microscope. These scales run along the nervures
and edges of the wings, and part of a nervure is shown more highly
magnified at Fig. 32.
At Fig. 23 is shown the wing of one of the hemipterous insects, common
along the banks of ditches and in shady lanes, and known by the name
of Cíxius. It is remarkable for the numerous spots which stud the
nervures, one being always found at each forking, and the others being
very irregularly disposed.
Fig. 30 is one of the balancers or “haltéres” of the house-fly. These
organs are found in all the two-winged insects, and are evidently
modifications of the second pair of wings. They are covered with
little vesicles, and protected at their base by scales. Some writers
suppose that the sense of smell resides in these organs. Whatever other
purpose they may serve, they clearly aid in the flight, as, if the
insect be deprived of one or both of the balancers, it has the greatest
difficulty in steering itself through the air.
The wings of insects are mostly covered with hairs or scales, several
examples of which are given in Plate VIII. Fig. 4 shows one of the
scales of the Adippe or fritillary butterfly, exhibiting the double
membrane--part of which has been torn away--and the beautiful lines of
dots with which it is marked. The structure of the scales is further
shown by a torn specimen of tiger moth scale seen on Fig. 16. On
many scales these dots assume a “watered” aspect when the focus or
illumination changes, an example of which may be seen in Fig. 15, a
scale of the peacock butterfly.
Fig. 11 is one of the ordinary scales of the azure blue butterfly,
and Fig. 10 shows one of the curious “battledore” scales of the same
insect, with its rows of distinct dottings. Fig. 14 is one of the
prettily tufted scales of the orange-tip butterfly, and Fig. 8 is the
splendid branched scale of the death’s-head moth. Fig. 19 shows a scale
of the sugar-runner (_Lepisma saccharína_), a little silvery creature
with glistening skin, and long bristles at the head and tail, that is
found running about cupboards, window-sills, and similar places. It
is not easy to catch with the fingers, as it slips through them like
oil; but by holding a cover-glass in a pair of forceps, and pressing it
upon one of the little creatures, a number of the scales may be caused
to adhere to it, and these should be mounted dry for examination. The
gnats also possess very pretty scales, with the ribs projecting beyond
the membrane.
VII.
FIG.
1. Tongue, Hive Bee
2. Do. Tortoiseshell Butterfly
3. Do. do. one of the barrel-shaped bodies
4. Head, Violet Ground Beetle (Carabus)
5. Tongue, Cricket
6. Do. do.
7. Head, Scorpion Fly (Panorpa)
8. Leg, Ant
9. Proleg, Caterpillar
10. Do. do. single hook
11. Proboscis, Fly
12. Do. do. “modified trachea”
13. Part of Foreleg of Water Beetle (Acilius)
14. Do. large sucker
15. Leg, long-legged Spider (Phalangium)
16. Do. Harvest-bug (Trombidium)
17. Do. Glow-worm
18. Do. Dung fly
19. Do. Asilus
20. Do. Acarus of Dor-beetle
21. Claws and Pad, Ophion
22. Wings, Humble Bee
23. Do.
24. Wing hooks, hind wing of Aphis
25. Wing hooks, Humble Bee
26. Foot, Flea
27. Stomach and gastric teeth, Bee
28. Three teeth of do.
29. Cast skin, Larva of Tortoise Beetle (Cassida)
30. Balancer, Blow fly
31. Wing, Midge (Psychoda)
32. Do. do. part of a nervure with scales
33. Stomach and gastric teeth, Grasshopper
34. Spiracle, Wire-worm
[Illustration: VII.]
Fig. 21 is a scale from the common spring-tail (_Podúra plúmbea_), a
little creature which is found plentifully in cellars and other damp
places, skipping about with great activity. Some flour scattered on a
piece of paper is a sure trap for these little beings. Fig. 3 is one
of the scales taken from the back of the celebrated diamond beetle,
showing the cause of the magnificent gem-like aspect of that insect. We
have in England many beetles of the same family--the weevils--which,
although much smaller, are quite as splendid when exhibited under a
microscope by reflected light. The wing-case or “elytron” of a little
green weevil, very common in the hedges, may be seen on Plate XII.
Fig. 10.
The reader will observe that all these scales are furnished with little
root-like appendages, by means of which they are affixed to the insect.
Fig. 13 shows a portion of the wing of the azure blue butterfly, from
which nearly all the scales have been removed, for the purpose of
exhibiting the pits or depressions in which they had formerly been
fastened, and one or two of the scales are left still adherent to their
places. The scales are arranged in equal rows like the slates of a
housetop, as may be seen on Fig. 18, which represents part of the same
wing, to show the scales overlapping each other, and the elegant form
which they take near the edges of the wing, so as to form a delicate
fringe. The long hair-like down which covers the legs and bodies of the
moths and butterflies (which are called Lepidóptera, or scale-winged
insects, in consequence of this peculiarity), is seen under the
microscope to be composed of scales very much elongated, as is shown in
Fig. 17, a portion taken from the leg of a tiger moth.
* * * * *
The eggs of insects are all very beautiful, and three of the most
curious forms are given on Plate VIII.
Fig. 2 is the empty egg of the gad-fly, as it appears when fastened to
a hair of the horse. Fig. 5 represents the pretty ribbed egg of the
common tortoise-shell butterfly; and Fig. 7 is the very beautiful egg
of the very horrid bed-bug, worthy of notice on account of the curious
lid with which its extremity is closed, by means of which the young
larva creeps out as soon as it is hatched.
The feathers of birds, and the fur of animals, will furnish many
examples of the eggs of parasites, some of which are of extreme beauty.
The feather or hair may be mounted in a cell without disturbing the
eggs, which should, however, be heated sufficiently to kill the embryo
if present.
Fig. 9 shows the penetrating portions of the sting of the wasp. The
two barbed stings, which seem to be the minute prototypes of the
many-barbed spears of the South Sea islanders, are seen lying one at
each side of their sheath, and a single barb is drawn a little to the
left on a very much larger scale. It is by reason of these barbs that
the sting is always left adhering to the wound, and is generally drawn
wholly out of the insect, causing its death in a short while.
The sting is only found in female insects, and is supposed to be
analogous to the “ovipositor” of other insects, _i.e._ the instrument
by which the eggs are deposited in their places. Fig. 20 shows the
curious egg-placing apparatus of one of the saw-flies. The backs of
these “saws” work in grooves, and they work alternately, so that the
fly takes but a very short time in cutting a slit in the young bark
of a tender shoot, and laying her eggs in the slit. When she has
completed one of these channels, she sets to work upon another, and in
the early spring the young branches of the gooseberry bushes may be
seen plentifully covered with these grooves and the eggs. When hatched,
black caterpillar-like grubs from the eggs issue, and devastate the
bushes sadly, turning in process of time into blackish flies, which are
seen hovering in numbers over the gooseberries, and may be killed by
thousands.
* * * * *
The scales and hairs of other animals deserve great attention. Fig. 23
is a single hair of the human beard, as it often appears when tied in
a knot--by Queen Mab and her fairies, according to Mercutio. Fig. 22
is a portion of the same hair as it appears when splitting at its
extremity. The structure of the hair is not, however, so well seen in
this object as in that represented on Fig. 24, which is a beautiful
example of white human hair that once adorned the head of the victor
of Waterloo. It formed one of a tiny lock given to me by a friend, and
is so admirable an example of human hair, that I forthwith mounted
it for the microscope. In this hair the cells may be seen extending
down its centre, and the peculiar roughened surface produced by the
flattened cells which are arranged around its circumference are also
seen. By steeping in caustic potash, these scales can be separated,
but generally they lie along the hair in such a manner that if the
hair be drawn through the fingers from base to point, their projecting
ends permit it to pass freely; whilst if it be drawn in the reverse
direction, they cause it to feel very harsh to the touch.
In the sheep’s wool (Fig. 30) this structure is much more developed,
and gives to the fibres the “felting” power that causes them to
interlace so firmly with each other, and enables cloth--when really
made of wool--to be cut without unravelling. Fig. 37 is the smooth hair
of the badger; and Fig. 34 is the curious hair of the red deer, which
looks as if it had been covered with a delicate net.
Fig. 28 is the soft, grey, wool-like hair of the rat; and Fig. 29
is one of the larger hairs that protrude so plentifully, and form
the glistening brown coat of that animal. Fig. 38 is the curiously
knobbed hair of the long-eared bat, the knobs being formed of
protuberant scales that can easily be scraped off. Fig. 31 shows a
hair of the common mole; and Fig. 32 is one of the long hairs of the
rabbit. Fig. 27 is a flat hair of the dormouse, slightly twisted, the
difference in the breadth showing where the twist has taken place. The
hair of the mouse is beautifully ribbed, so as to look like a ladder.
Fig. 26 is one of the very long hairs that so thickly clothe the tiger
moth caterpillar; and Fig. 25 is a beautifully branched hair taken from
the common humble bee.
All hairs should be examined by polarised light, with a plate of
selenite, when most gorgeous colour effects may be obtained.
The four fibres mostly used in the manufacture of apparel are: wool,
Fig. 30, which has already been described; linen, Fig. 39; cotton,
Fig. 40; and silk, Fig. 41. The structure of each is very well marked
and easily made out with the microscope; so that an adulterated article
can readily be detected by a practised eye. Cotton is the most common
adulteration of silk and linen fabrics, and may at once be detected
by its flat twisted fibre. Silk is always composed of two parallel
threads, each proceeding from one of the spinnerets of the caterpillar,
and it may be here remarked that if these threads are not quite
parallel the silk is of bad quality. Silken fibre is always covered,
when new, with a kind of varnish, usually of a bright orange colour,
which gives the undressed “floss” silk its peculiar hue, but which is
soluble and easily washed away in the course of manufacture.
Figs. 35 and 36 are the small and large hairs of that magnificent
creature, the sea mouse (_Aphrodíte aculeáta_), whose covering,
although it lies in the mud, glows with every hue of the rainbow, and
in a brilliant light is almost painfully dazzling to the eye.
VIII.
FIG.
1. Boat-fly, leg
2. Gadfly, empty egg
3. Diamond Beetle, scale
4. Scale, Fritillary, Adippe
5. Egg, Tortoiseshell Butterfly
6. Head and Eyes, Zebra Spider
7. Eyes, Bed-Bug
8. Scale, Death’s-Head Moth
9. Sting, Wasp
10. Scale, battledore, Azure blue
11. Do. ordinary scale
12. Eye, Harvest Spider
13. Wing Membrane, Azure Blue
14. Scale, Anthocera cardaminis
15. Do. Peacock Butterfly
16. Do. Tiger Moth
17. Do. Thigh of Tiger Moth
18. Wing and Scales, Azure Blue
19. Scale, Lepisma
20. Saws, Sawfly
21. Scale, Podura
22. Hair, Black Human
23. Do. Human Beard
24. Do. do. aged
25. Do. Humble Bee
26. Do. Tiger Moth, Larva
27. Do. Dormouse
28. Do. Rat
29. Do. do. long hair
30. Do. Sheep
31. Do. Mole
32. Do. Rabbit
33. Scale, Greenbone Pike
34. Hair, Red Deer
35. Do. fine, Sea Mouse
36. Do. do. large
37. Do. do. Badger
38. Do. do. long-eared Bat
39. Fibre, Linen
40. Do. Cotton
41. Do. Silk
42. Scale, Perch
43. Do. do.
[Illustration: VIII.]
The scales of some of the fishes are shown on Plate VIII., in order
to exhibit their mode of growth by successive layers. The scales are
always enveloped in membranous sacs, and in some cases, as in the
eel, they do not project beyond the surface, and require some little
observation to detect them. A scale of an eel is shown on Plate XI.
Fig. 14, and is a magnificent object under polarised light. Fig. 33
is a scale of the greenbone pike; and Figs. 42 and 43 are scales of
the perch, showing the roots by which they are held in their places.
The roach, dace, bleak, and many other similar fish have a beautiful
silvery substance on the under surface of the scales, which was greatly
used in the manufacture of artificial pearls, glass beads being thinly
coated in the interior with the glittering substance, and then filled
in with wax. A piece of sole-skin, when preserved in Canada balsam and
placed under the microscope, is a very beautiful object.
More examples of hairs, and other processes from the skin, together
with the structure of the skin itself, of bone, of blood, and the mode
in which it circulates, are given on Plate X.
In all important points of their structure the feathers of birds
are similar to the hairs of animals, and are developed in a similar
manner. They are all composed of a quill portion, in which the pith
is contained, and of a shaft, which carries the vane, together with
its barbs. The form of each of these portions varies much, even in
different parts of the same bird, and the same feather has almost
always two kinds of barbs; one close and firm, and the other loose,
floating, and downy. If a small feather be plucked from the breast
or back of a sparrow or any other small bird, the upper part of the
feather is seen to be close and firm, while the lower is loose and
downy, the upper part being evidently intended to lie closely on the
body and keep out the wet, while the lower portion affords a soft and
warm protection to the skin.
Fig. 12, Plate X., shows the feather of a peacock, wherein the barbs
are very slightly fringed and lie quite loosely side by side. Fig. 18
is part of the same structure, in a duck’s feather, wherein are seen
the curious hooks which enable each vane to take a firm hold of its
neighbour, the whole feather being thus rendered firm, compact, and
capable of repelling water. The reader will not fail to notice the
remarkable analogy between these hooks and those which connect the
wings of the bee.
Fig. 17 is a part of the shaft of a young feather taken from the
canary, given for the purpose of showing the form of the cells
of which the pith is composed. Fig. 20 is part of the down from a
sparrow’s feather, showing its peculiar structure; and Fig. 21 is a
portion of one of the long drooping feathers of the cock’s tail.
Fig. 13 exhibits a transverse section of one of the large hairs or
spines from the hedgehog, and shows the disposition of the firm,
horn-like exterior, and the arrangement of the cells. Sections of
various kinds of hair are interesting objects, and are easily made by
tying a bundle of them together, soaking them in gum, hardening in
spirit, and then cutting thin slices with a razor. A little glycerine
will dissolve the gum, and the sections of hair will be well shown.
Unless some such precaution be taken, the elasticity of the hair will
cause the tiny sections to fly in all directions, and there will be no
hope of recovering them.
Several examples of the skin are also given. Fig. 27 is a section
through the skin of the human finger, including the whole of one of the
little ridges which are seen upon the extremity of every finger, and
half of two others. The cuticle, epidermis, or scarf-skin, as it is
indifferently termed, is formed of cells or scales, much flattened and
horny in the upper layers, rounder and plumper below. The true skin,
or “cutis,” is fibrous in structure, and lies immediately beneath, the
two together constituting the skin, properly so called. Beneath lies a
layer of tissue filled with fatty globules, and containing the glands
by which the perspiration is secreted.
One of the tubes or channels by which these glands are enabled to
pour their contents to the outside of the body, and, if they be kept
perfectly clean, to disperse them into the air, is seen running up
the centre of the figure, and terminating in a cup-shaped orifice on
the surface of the cuticle. On the palm of the hand very nearly three
thousand of these ducts lie within the compass of a square inch, and
more than a thousand in every square inch of the arm and other portions
of the body, so that the multitude of these valuable organs may be well
estimated, together with the absolute necessity for keeping the skin
perfectly clean in order to enjoy full health.
Fig. 1 shows a specimen of epidermis taken from the skin of a frog,
exhibiting the flattened cells which constitute that structure, and
the oval or slightly elongated nuclei, of which each cell has one. In
Fig. 32, a portion of a bat’s wing, the arrangement of the pigment
is remarkably pretty. Immediately above, at Fig. 31, is some of the
pigment taken from the back of the human eye-ball. The shape of the
pigment cells is well shown. Similar specimens may easily be obtained
from the back of a sheep’s eye which has been hardened in spirit, or
from that of a boiled fish. Fig. 33 shows the pigment in the shell of
the prawn.
* * * * *
On various parts of animal structures, such as the lining of internal
cavities, the interior of the mouth, and other similar portions of
the body, the cells are developed into a special form, which is
called “Epithélium,” and which corresponds to the epidermis of the
exterior surface of the body. The cells which form this substance are
of different shapes, according to their locality. On the tongue, for
example (for which see Fig. 11), they are flattened, and exhibit their
nucleus, in which the nucléolus may be discovered with a little care.
Cells of this kind are rounded, as in the case just mentioned, or
angular, and in either case they are termed squamous (_i.e._, scaly)
epithelium. Sometimes they are like a number of cylinders, cones, or
pyramids, ranged closely together, and are then called cylindrical
epithelium. Sometimes the free ends of cylindrical epithelium are
furnished with a number of vibrating filaments or cilia, and in this
case the structure is called “ciliated” epithelium. Cylindrical
epithelium may be found in the ducts of the glands which open into
the intestines, as well as in the glands that secrete tears; and
ciliated epithelium is seen largely in the windpipe, the interior of
the nose, etc. A specimen taken from the nose is seen at Fig. 15. A
beautiful example of ciliated epithelium is to be found in the gills
of the mussel. A portion of one of the yellowish bands which lie along
the edge of the shell on the opening side is carefully removed with
sharp scissors, and examined in the shell-liquor, being protected
from pressure by placing a piece of paper beneath each end of the
cover-glass. Such a preparation is shown in Plate IX. Fig. 39, but no
drawing can give an idea of its wonderful beauty and interest. The
cilia will continue to move for a long time after removal from the
shell.
* * * * *
Bone in its various stages is figured on Plate X.
Fig. 9 is a good example of human bone, and is a thin transverse
section taken from the thigh. When cut across, bone exhibits a whitish
structure filled with little dottings that become more numerous towards
the centre, and are almost invisible towards the circumference. In the
centre of the bone there is a cavity, which contains marrow in the
mammalia and air in the birds. When placed under a microscope, bone
presents the appearance shown in the illustration.
The large aperture in the centre is one of innumerable tubes that run
along the bone, and serve to allow a passage to the vessels which
convey blood from one part of the bone to another. They are technically
called Haversian canals, and if a longitudinal section be made they
will be found running tolerably parallel, and communicating freely
with each other. Around each Haversian canal may be seen a number of
little black spots with lines radiating in all directions, and looking
something like flattened insects. These are termed bone-cells or
“lacúnæ,” and the little black lines are called “canalículi.” In the
living state they contain cells which are concerned in the growth of
the bone, and these may be made evident by softening fresh bone with
acid, cutting sections of it, and staining. When viewed by transmitted
light the lacunæ and canaliculi are black; but when seen by dark-field
illumination the Haversian canals become black, and the lacunæ are
white.
As these canaliculi exist equally in every direction, it is impossible
to make a section of bone without cutting myriads of them across; and
when a high power is employed they look like little dots scattered over
the surface. A very pretty object can be made of the bone taken from a
young animal which has been fed with madder, as the colour gets into
the bone and settles chiefly round the Haversian canal. A young pig is
a very good subject, so is a rabbit.
Fig. 16 is a similar section cut from the leg-bone of an ostrich.
The development of bone is beautifully shown in Fig. 30, a delicate
slice taken from a pig’s rib. Above may be seen the gristle or
cartilage, with the numerous rows of cells; below is the formed bone,
with one of the Haversian canals and its contents; while between the
two may be seen the cartilage-cells gathering together and arranging
themselves into form. The cartilage-cells are well shown in Fig. 28,
which is a portion of the cup which had contained the eye of a haddock.
The horn-like substances at the end of our fingers, which we call the
nails, are composed of innumerable flattened cells. These cells are
generally so fused together as to be quite indistinguishable even with
a microscope, but can be rendered visible by soaking a section of nail
in liquor potassæ, which causes the cells to swell up and resume to a
degree their original rounded form.
It is worthy of remark that the animal form is built up of cells, as is
the case with the vegetables, although the cells are not so variable
in shape. They generally may be found to contain well-marked nuclei,
two or more of the latter being often found within a single cell, and
in many cases the tiny nucleoli are also visible. Good examples of
these cells may be obtained from the yolk of an egg, and by careful
management they may be traced throughout every part of the animal form.
The teeth have many of the constituents of bone, and in some of their
parts are made after precisely the same fashion. When cut, the teeth
are seen to consist of a hard substance, called enamel, which coats
their upper surfaces, of dentine, or ivory, within the enamel, and of
“cement,” which surrounds the fangs. In Fig. 26, Plate X., which is
a longitudinal section of the human “eye” tooth, is seen the ivory
occupying the greater part of the tooth, coated by the enamel at the
top and the cement at the bottom. In the centre of each tooth there is
a cavity, which is plentifully filled with a pulpy substance by which
the tooth is nourished, and which conveys the nerves which endow it
with sensation. A traverse section of the same tooth is seen in Fig. 25.
The enamel is made of little elongated prisms, all pointing to the
centre of the tooth. When viewed transversely, their ends are of a
somewhat hexagonal shape, something like an irregular honeycomb. The
dentine is composed of a substance pierced with myriads of minute
tubes. They require a rather high power--say 300 diameters--to show
them properly. The cement is found at the root of the fangs, and is
best shown in the tooth of an aged individual, when it assumes very
clearly the character of bone.
Sections may be made by sawing a slice in the required direction,
polishing one side, and cementing it with old Canada balsam to a slide.
It may then be filed down to nearly the required thinness, finished by
carefully rubbing with a hone, and polished with buff leather. Canada
balsam may then be dropped upon it, and a glass cover pressed firmly
down.
Sections of young bone form magnificent objects for the polariser.
Fig. 29 is a section cut from one of the palate teeth of the ray
(_Myliobátes_).
A rather important element in the structure of animals is the “elastic
ligament,” which is found in the back of the neck and other parts of
the body, especially about the spine. It is made of a vast number of
fibres of variable shape and length, branching and communicating,
arranged generally in bundles, and remarkable for containing very few
vessels, and no nerves at all. At Fig. 14 may be seen an example of
elastic ligament, popularly called “paxwax,” taken from the neck of a
sheep.
The white fibrous tissue by which all the parts of the body are bound
together is seen at Fig. 10; and at Fig. 11 is a beautiful example of
the “ultimate fibres” of the crystalline lens of a sturgeon’s eye.
The muscles of animals are of two kinds, the one termed the striped,
and the other the unstriped. Of these, the latter belongs to organs
which work independently of will, such as the stomach, etc., while
the former belongs to those portions of the body which are subject to
voluntary motion, such as the arm and the leg. The unstriped muscle
is very simple, consisting merely of long spindle-shaped cells, but
the striped or voluntary muscle is of more complex construction. Every
voluntary muscle consists of myriads of tiny fibres, bound together in
little bundles, enveloped in a kind of sheath. Fig. 24 is an example of
this muscular fibre, taken from beef. When soaked in spirit, it often
splits into a number of discs, the edges of which are marked by the
transverse lines.
A fibre of nerve is drawn at Fig. 23, and is given for the purpose of
showing the manner in which the nerve is contained in and protected
by its sheath, just like a telegraph-wire in its coverings. Just
above is a transverse section of the same fibre, showing the same
arrangement from another point of view, and also illustrating the
curious phenomenon, that when nerve-fibres are treated with carmine the
centre takes up the colouring matter, while the sheath remains white as
before. The best way of studying nerves is to decapitate a frog, and
cut off a piece of one of the nerves, which, like fine silk threads,
come out between the joints of the spine inside the abdomen. By careful
teasing out it is easy to obtain preparations showing all the above
points, and, in addition, the folding-in of the internal sheath which
correspond to the insulators of a telegraph-line.
The blood of animals is analogous in its office to the sap of plants,
but differs greatly from it under the microscope. In sap there seem to
be no microscopic characters, except that when a branch is cut, as in
the vine, the flowing sap may contain certain substances formed in the
wounded cells, such as chlorophyll, starch, and raphides; but the blood
is known to be an exceedingly complex substance both in a microscopic
and a chemical point of view. When a little fresh blood is placed under
the microscope, it is seen to consist of a colourless fluid filled with
numerous little bodies, commonly called “blood-globules,” varying very
greatly in size and shape, according to the animal from which they
were taken. Those of the reptiles are very large, as may be seen at
Fig. 4, Plate X., which represents a blood corpuscle of the Proteus.
In this curious reptile the globules are so large that they may be
distinguished during its life by means of a common pocket lens.
In the vertebrated animals these corpuscles are red, and give to the
blood its peculiar tint. They are accompanied by certain colourless
corpuscles, spherical in form, which are sometimes, as in man, larger
than the red globules, and in others, as in the siren and the newt,
considerably smaller. The general view of the red corpuscles has
sufficient character to enable the practised observer to name the
class of animal from which it was taken, and in some cases they are
so distinctive that even the genus can be ascertained with tolerable
certainty. In point of size, the reptiles have the largest and the
mammalia the smallest, those of the Proteus and the musk-deer being
perhaps the most decidedly opposed to each other in this respect.
IX.
FIG.
1. Amœba diffluens
2. Arcella
3. Sun animalcule
4. Miliolina
5. Paramœcium
6. Chilodon subdividing
7. Melicerta ringens
8. Spicula of Sponge, Grantia
9. Noctiluca miliaris
10. Rotifer vulgaris
11. Do. jaws
12. Sponge animalcule
13. Sertularia operculata
14. Sponge, Grantia
15. Sertularia operculata, with ovicells
16. Actinia, showing weapons
17. Do. base of weapon more magnified
18. Sponge granule, ciliated
19. Anguinaria anguina
20. Spicules of sponge from Oyster Shell
21. Head of Snake-headed Zoophyte
22. Bugula avicularia
23. Polyzoön, Eretea
24. Do. Notamia
25. Zoea, Young of Crab
26. Hydra tuba
27. Medusa, cast off from above
28. Naked-eyed Medusa, Thaumantias
29. Compound Eye, Medusa
30. Larva, Snake Star
31. Water Flea
32. Serpula, Pushing Pole
33. Comatula, early stage of Starfish
34. Carbonate of Lime, artificial
35. Sea Urchin, transverse section of spine
36. Serpula, bundle of spears
37. Sun-star, part of skin
38. Oyster shell in different stages
39. Cilia on mussel
[Illustration: IX.]
In shape, those of the mammalia are circular discs, mostly with a
concave centre, though the camel has oval ones; those of the birds are
more or less oval and convex; those of the reptiles are decidedly oval,
very thin, and have the nucleus projecting; and those of the fishes are
oval and mostly convex. During the process of coagulation the blood
corpuscles run together into a series of rows, just as if a heap of
pence had been piled on each other and then pushed down, so that each
penny overlaps its next neighbour.
These objects are illustrated by six examples on Plate X. Fig. 2 is
human blood, showing one of the white corpuscles; Fig. 3 is the blood
of the pigeon; Fig. 4, of the _Proteus anguínus_; Fig. 5, of the
tortoise; Fig. 6, of the frog, showing the projecting nucleus; and
Fig. 7, of the roach. The blood possesses many curious properties,
which cannot be described in these few and simple pages.
In the centre of Plate X. is a large circular figure representing
the membrane of a frog’s foot as seen through the microscope, and
exhibiting the circulation of the blood. The mode of arranging the foot
so as to exhibit the object without hurting the frog is simple enough.
Take an oblong slip of wood,--my own was made in five minutes out of
the top of a cigar-box,--bore a hole about an inch in diameter near
one end, and cut a number of little slits all round the edge of the
wooden slip. Then get a small linen bag, put the frog into it, and dip
him into water to keep him comfortable. When he is wanted, pull one of
his hind feet out of the bag, draw the neck tight enough to prevent
him from pulling his foot back again, but not sufficiently tight to
stop the circulation. Have a tape fastened to the end of the bag, and
tie it down to the wooden slide. Then fasten a thread to each of his
toes, bring the foot well over the centre of the hole, stretch the toes
well apart, and keep them in their places by hitching the threads into
the notches on the edge of the wooden strip. Perhaps an easier plan
is to secure the threads by drops of sealing-wax when in the desired
position. Push a glass slide carefully between the foot and the wood,
so as to let the membrane rest upon the glass, and be careful to keep
it well wetted. If the frog kick, as he will most likely do, pass a
thin tape over the middle of the leg, and tie him gently down to the
slide.
Bring the glass into focus, and the foot will present the appearance
so well depicted in the engraving. The veins and arteries are seen
spreading over the whole of the membrane, the larger arteries being
often accompanied by a nerve, as seen in the illustration. Through all
these channels the blood continually pours with a rather irregular
motion, caused most probably by the peculiar position of the reptile.
It is a most wonderful sight, of which the observer is never tired,
and which seems almost more interesting every time that it is beheld.
The corpuscles go pushing and jostling one another in the oddest
fashion, just like a British crowd entering an exhibition, each one
seeming to be elbowing its way to the best place. To see them turning
the corners is very amusing, for they always seem as if they never
could get round the smaller vessels, and yet invariably accomplish the
task with perfect ease, turning about and steering themselves as if
possessed of volition, and insinuating their ends when they could not
pass crosswise.
By putting various substances, such as spirit or salt, upon the
foot, the rapidity of the circulation at the spot can be greatly
increased or reduced at will, or even stopped altogether for a while,
and the phenomenon of inflammation and its gradual natural cure be
beautifully illustrated. The numerous black spots upon the surface are
pigment-cells.
The tails of young fish also afford excellent objects under the
microscope, as the circulation can be seen nearly as well as in the
frog’s foot. The gills of tadpoles can also be arranged upon the stage
with a little care, and the same organs in the young of the common newt
will also exhibit the circulation in a favourable manner. The frog,
however, is perhaps the best, as it can be arranged on the “frog-plate”
without difficulty, and the creature may be kept for months by placing
it in a cool, damp spot, and feeding it with flies, little slugs, and
similar creatures.