beautiful microscopic object, viewed either as transparent or opake.
The spider has eight legs with three joints, thickly beset with hairs,
and terminating in three crooked moveable claws, which have little teeth
like a saw; at a small distance from these claws, but placed higher up,
is another something like a cock’s spur, by the assistance of which it
adheres to its webs; but the weapon wherewith it seizes and kills its
prey is a pair of sharp crooked claws or forceps placed in the fore-part
of the head. The insect can open or extend these pincers as occasion may
require; when undisturbed, it suffers them to lie one upon another,
concealed in two cases constructed for their reception. Leeuwenhoeck
says, that each of these claws has a small aperture or slit, through
which he supposes a poisonous juice is injected into the wound it makes.
The exuvia, or cast-off skin of the spider, which may be found in
cobwebs, being transparent, is an excellent object; and the fangs or
forceps may be more easily separated from it, and examined with greater
exactness than in a living subject. The contexture of the spider’s web,
and the manner of weaving it, have been discovered by the microscope.
The spider is supplied with a large quantity of glutinous matter within
its body, and five tubercles or nipples for spinning it into thread, of
what size it pleases, either by opening or contracting the sphincter
muscles. This substance, when examined accurately, will be found twisted
into many coils, of an agate colour, and which from its tenacity may be
easily drawn out into threads. The five nipples are placed near the
extremity of the tail; from these the aforesaid substance proceeds; it
adheres to any thing against which it is pressed, and being drawn out
hardens in the air. The threads unite at a small distance from the body,
so that those which appear to us so fine and single, are,
notwithstanding, composed of five joined together, and these are many
times doubled when the web is in formation. The web serves him for the
double purpose of an habitation and of a machine for catching his food;
for in the center of this web it dwells in dismal solitude, like a
dragon in his lonely den, an image of the evil one, wasting all things
round about it, and eager to destroy every appearance of life. When
first hatched, even these loathsome insects seem endued with a principle
of association, spinning a web in common; but this connection is of
short duration, and soon terminates by their destroying one another. If,
like the silk-worm, they were disposed to live together peaceably, it is
possible that their labours might be productive of advantages nearly
similar to that valuable insect; for which purpose repeated attempts
have been made, though they proved ineffectual.
OF THE CULEX, OR GNAT.
The gnat is a beautiful object for the microscope. The curious manner in
which it disposes its eggs upon the surface of the water has been
noticed in page 288. From the egg proceeds the larva, in which state it
is most happily suited to shew the several operations of life; for a
moderate magnifying power will discover what passes within its
transparent body. It has a large scaly head, with two large antennæ,
besides several hairy parts, and articulated bristles near the mouth,
which are in continual motion. If the worm be dissected, the feet of the
gnat may be found folded up in the divisions of the thorax; the abdomen
is divided into eight rings, from the edges of each of which three or
four bristles proceed. The tail is divided into two parts of very
different forms; by one of these it can steer itself in any direction;
in the other, two pulmonary tubes may be discovered, through which the
insect breathes. The larva has a power of moistening the tail with an
oleaginous liquor, by which means it can suspend itself on the surface
of the water. On agitating the water, the worms descend with
precipitation to the bottom; but they soon return to the surface, to
breathe the air through the tube that is annexed to their tail. From
this state, they pass into that of the pupa, which is the gnat enclosed
in a third skin, under which it is formed and strengthened; the organs
of respiration are changed, breathing at this period through a couple of
horns, which are placed near the head, keeping itself rolled upon the
surface of the water, though on the least motion it unrolls itself and
descends, aided by the oars near the tail.
From the spoils of the pupa, a little winged insect proceeds, whose
every part is active to the highest degree, and whose entire structure
is the just object of our admiration. Its head, adorned with feathers,
is a fine microscopic object; but the proboscis may be deemed one of the
most curious instruments in the insect creation. This formidable
apparatus has been particularly described in page 187.
The exuviæ or cast-off skins of insects, being exceedingly transparent,
are well adapted for observation, as they exhibit the external
appearance of the little animal; among these, may be reckoned those of
spiders and cimices, but particularly the forficula auricularia or
earwig, which is an elegant exuvia; a magnified view of the beautiful
wing of this insect is exhibited in Plate XIV. and described in page
205. The stings of insects vary not only in their form, but also in
their apparatus; most of them require dissection; as the stings, for
they have generally two, are inclosed in a hard sheath or case, to which
is added a pair of feelers. The stings of bees, wasps, &c. are barbed,
while those of the chrysis are serrated, or notched like a saw. The head
of insects is furnished with an instrument or proboscis various as the
insects themselves, but all meriting attention, as being admirably
adapted to their different uses and purposes. Among the most remarkable
are those of the bed bug, flea, gnat, empis, conops, &c. to which may
be added the singular one of the tabanus, described in page 188, and
figured in Plate XVI. A description of the apparatus of the bee has also
been given in page 181, and of that of the butterfly in page 186.
The antennæ of moths, butterflies, and most other insects, display as
great beauty in their formation as they are endless in their variety;
the distinguishing characters of many of them have been described in
pages 190-193, and that of the lepas anatifera in particular in page
345, and exhibited in Plate XIII.
The eyes of insects are singularly constructed, but this structure is
not discoverable without the assistance of the microscope; the eyes of
the libellula are hexagonal, see Plate XVI. Fig. 3, and their
description in page 195; those of the lobster are square, as exhibited
in Fig. 5 of the same plate, and described in page 197.
The hair of animals, as the mouse, goat, large bee, and many species of
caterpillars, particularly the tufts on the head and tail of the larva
of the phalæna antiqua, offer many beauties to the curious observer. The
bristles of a hog, cut transversely, appear tubular, and the root of
hair is evidently bulbous.
The muscular fibres, and every anatomical preparation that can be
brought under the microscope, are pleasing objects; the reader will meet
with many curious and interesting observations on the hairs, the
muscles, nerves, and other parts of the human body, in Fontana’s
Treatise on the Venom of Vipers.
The legs of all insects appear very much diversified, and their
mechanism truly astonishing, according with their different occupations,
as particularized in pages 210-212.
Scales of fish, as soles, roach, dace, salmon, eels, &c. as also the
scales of snakes, lizards, &c. &c. Specimens of scales are given in
Plates X. and XIX. The scales form a light, but at the same time a solid
and smooth covering to the fish; they hinder the fluid from penetrating
the body, for which purpose they are laid in a kind of natural oil; they
serve also as a protection, and break the force of any accidental blow,
which may be the reason why river-fish have larger and stronger scales
than sea-fish, being more liable to accidents.
The purple tide of life, nay the very globules of the blood, may be seen
distinctly rolling through veins and arteries smaller than the finest
hair.[151]
[151] The manner of viewing the particles of the blood has been
described in p. 149, together with some remarks on their form, by our
author. It was not my intention to have renewed the subject; but a
chirurgical treatise having been lately published by Everard Home,
Esq. F. R. S. in which it appears that he has paid particular
attention towards investigating these minute particles, and
ascertaining their true form, I shall here subjoin an abstract.
“As the result of microscopical experiments has been found exceedingly
fallacious, a prejudice has very naturally arisen against all
experiments of this kind upon the secretions of the human body, from a
supposition that they are not to be depended upon. But it is right
that we should discriminate, and not condemn the use of the microscope
altogether, because from ignorance of its principles it has been
misapplied; since these very deceptions have been the means of our
acquiring a more accurate knowledge of the use and application of that
instrument.
“The errors in the use of the microscope have arisen from increasing
the magnifying powers of the glasses too much, and not taking in all
the circumstances relating to the refraction of the rays of light,
making no allowance for the aberration. An attention to the aberration
alone will explain the different appearances under which the red
globules of the blood have been represented. Some have found them
perfect spheres, which will always be the case when the glasses are
perfectly adjusted, and the object placed at the true focal distance.
Others have found them annular, from the object being at the focal
distance of the rays transmitted near the circumference of the
magnifying glass, which are refracted in a greater degree, and
consequently shorter than the central rays. Others, again, have viewed
them as flattened bodies of a circular figure, bright in the center,
and becoming darker towards the edges; which appearance arises from
the object being at the focal distance of the central rays of the
magnifying glass, which will be less refracted than those near the
circumference. Although such are the errors which arise, when
microscopical researches are pushed beyond certain bounds; yet, that
the red part of the blood is made up of globules, is a discovery for
which we are indebted to the microscope, and which seems to be as well
ascertained as any discovery in anatomy or physiology. The appearances
of pus are equally distinct, when examined on the field of a
microscope, as the globules of the blood; they are visible with a
small degree of magnifying power, and are the same to the eyes of
different persons.” EDIT.
Feathers, and parts of feathers of birds, are not to be passed by or
unnoticed; but it is impossible to point out any of these in preference
to others, as each has its peculiar beauties; the plumulæ of these have
generally in the microscope the appearance of large feathers; the pith
contained in the quill, if cut transversely and examined, exhibits an
admirable reticular texture. Many other parts of birds will afford a
great variety of curious objects, particularly the egg: Mr. Martin says,
that the internal spongy substance of bones may be better observed in
those of birds, than of any other animal; even the feathers or scales of
a moth’s wing amply repay the observer; these also vary in their texture
and figure; but the largest and most commonly applied, are from the body
of the sphinx stellatarum, or humming-bird moth; a specimen is given in
Plate XVI. Fig. E F H I.
Transverse sections of all kinds of wood, especially those of a pithy or
soft nature, form some of the most delightful objects for the
microscope; among these, the section of fern root will be found
strikingly curious, from the singular disposition of the air and sap
vessels; their beauty will be seen by the figures in Plates XXVIII.
XXIX. and XXX.
Flowers, whose brilliancy and variety constitute one of the principal
beauties of nature, each being distinguished from the rest by some
peculiar beauty or shining character.
The flowers of most grasses, with all the varieties of mosses; the
farina of flowers; mouldiness, which evidently appears to vegetate; all
the kinds of sponge; sea-weeds; particularly the confervæ, which are
jointed like a cane. The extensive family of corallines present an
elegant appearance; the most beautiful are the sea hair, sea fir,
sickle, fox tail, &c. described by Ellis.
Dissected leaves, which shew the fibres and nerves; the human intestine
injected with wax is a fine object; as are many other anatomical
preparations. The seed of the silver-rind birch appears like an insect;
seed of the quaking grass is also much admired, as is the leaf which
covers the seed of sorrel. Among artificial productions, the edge of a
razor, and point of a fine needle, as also fine cambrick, evidently
discover the inferiority of the workman; particles from the collision of
flint and steel; wire melted by the electric explosion, and other
articles innumerable.
Besides these, there is an immense variety of objects which can only be
satisfactorily examined alive, such as polypes, minute aquatic insects;
animalcula of various infusions, as eels in paste, vinegar, &c. The eyes
and teeth of snails; the circulation of the blood in the tails of
fishes, &c.[152]
[152] Those who possess leisure, particularly such who reside in the
country, may easily procure the major part of the preceding objects,
and also add an extensive variety to them; but those who have not the
opportunity of collecting for themselves, may be supplied with objects
in considerable variety by application to Messrs. Jones. EDIT.
CHAP. XI.
AN ARRANGEMENT AND DESCRIPTION OF MINUTE AND RARE SHELLS.--A DESCRIPTIVE
LIST OF A VARIETY OF VEGETABLE SEEDS, AS THEY APPEAR WHEN VIEWED BY THE
MICROSCOPE. BY THE EDITOR.
Notwithstanding the abundance of objects which have from time to time
afforded delight to the attentive and diligent microscopic observer,
little doubt can be entertained but that amidst the immense variety of
minute shells, as well as the seeds of vegetables, numbers remain
unexplored, though highly meriting notice.
With the hope of exciting the attention of the curious toward these
subjects, and affording hints to those who may happily possess
inclination, together with leisure and opportunity to pursue the
inquiry, I shall enumerate to the reader a few specimens of each of
these admirable productions of nature; towards the elucidating of which,
very little, comparatively, has as yet been done.
As far as my knowledge extends, the first author who has treated on the
subject of minute and rare shells, is Plancus, who published a treatise
in quarto, at Venice, in the year 1739, with the title “De Conchis
Ariminensibus minus notis;” a third and improved edition of which
appeared in 1760. It is a very curious and learned work, containing a
natural history of testaceous animals of Rimini, an Italian town
situated on the Adriatic shore; and more particularly of minute nautili.
In the year 1784, Mr. Walker of Faversham published in quarto a
collection of minute shells, which was the joint production of himself
and William Boys, Esq. F. S. A. of Sandwich, in Kent, assisted by the
late Edward Jacob, Esq. F. S. A. It contains an arrangement and concise
description of ninety shells, accompanied with neatly engraved figures
of the whole series; the greater part of them as well in their magnified
state, as that in which they appear to the naked eye. Specimens of those
which are esteemed most curious and rare, I have selected from this
work: a reference to the original will afford the reader more complete
satisfaction, and possibly animate him to further pursuits.
This publication appeared in so favourable a light to that eminent
patron of science, Sir Joseph Banks, that I should accuse myself of
unjustifiable remissness, were I to neglect this opportunity of
introducing an extract from the copy of a letter addressed by him to the
late Mr. Jacob, which is now in my possession.
“We” (the Royal Society) “are all much obliged to you for the pains you
have taken in bringing this work to light. Natural history is, I am
convinced, more benefited by a thin volume of real new facts, which is
the case in yours, than by a folio of comments generally written by
those who mean to receive praise, more founded on the elegance with
which they express the ideas they conceive, than on any prospect of
utility to be derived from the ideas themselves. From such naturalists,
De Buffon, &c. good Lord deliver our honest science.”
That truly amiable, and no less intelligent lady, the late Duchess
Dowager of Portland, likewise expressed her approbation of the work in a
letter to Mr. Boys.
By this publication, a number of shells, heretofore unknown, are added
to the British conchology, sufficient to shew that the path is now laid
open and made easy of access to inquisitive naturalists in different
parts of the kingdom for still greater discoveries. Indeed, it is rather
extraordinary, that the authors of this country, who have so
advantageously applied the microscope to a variety of objects in the
animal kingdom, should have neglected to examine the shores of our own
seas, crowded as they are with objects equally worthy of their
investigation. Baker’s observation in his “Employment for the
Microscope,” p. 244, is entitled to more attention than has been paid to
it. “Shell-fish,” says he, “are objects that have as yet been very
slightly examined by the microscope, and therefore the serious inquirer
into nature’s secret operations may here be certain of discovering
beauties, which at present he can have no conception of.” But thus it
is, nature opens her rich and inexhaustible treasures by slow degrees to
the inquisitive mind of man. In fact, different observers have generally
different pursuits, otherwise these objects would scarcely have escaped
the attention of many ingenious naturalists, particularly the
quick-sighted Mr. Ellis, who has so clearly investigated and described
the corals and corallines of the adjacent coasts.
To those who have perused the treatise of Plancus, already mentioned, it
is necessary to observe, that though the sand on our coasts contain a
vast variety of specimens, yet it by no means appears so productive as
the sand of Rimini; lest, despairing of success in their first
researches, they may be induced to desist from further examination.
Every parcel will, however, be found to contain some of the more common
shells.
It may not be improper here to point out to future inquirers the mode of
facilitating the discovery of these minute objects. The sand being
perfectly dried, put a handful on an open sheet of paper, and by gently
shaking it from side to side, the minute shells, being specifically
lighter than the sand, will be separated from, and lie on its surface,
and will thus be more expeditiously procured than by any other method.
It is also adviseable to place the objects intended for inspection in a
situation secured from any sudden blast of air, otherwise, owing to
their levity, they may be unexpectedly blown away, and a loss sustained
of some of the rarer specimens; even incautiously breathing on them, or
coughing, may be productive of similar disagreeable effects.
The following observations by an ingenious critic[153] are so apposite,
and so perfectly coincident with my own sentiments on the subject, that
I cannot resist the impulse I feel to enable the reader to partake of
the pleasure which I have experienced in their perusal.
[153] Monthly Review, Vol. LXXI. p. 190.
“Let not the minuteness of the objects here delineated call up the surly
inquiries of those, who have not been accustomed to live with their eyes
open to the works of nature: they are not fit judges in these matters.
If they will persist in asking, Of what use is all this labour? What
good can accrue to mankind from this knowledge, in point of food, or
other use? We know of none at all, either present or likely to happen,
as to the body, for use or ornament, or to the satisfying any appetite:
nevertheless, a much nobler idea will take its rise in our opinion; one
which, by displaying so momentously the power of the omniscient Creator,
will thwart the infidel in his favourite ideas of escaping the eyes of
the Almighty, and force him, as he descends the scale from the more
immense objects to these minutissima, to confess, that the being which
has formed these, can fully equal all that the tongue of man has yet
declared of the possibility of his power. For, what a train of wonders
have we here to pursue? What must be the œconomy of animals so very
diminutive, so weak, so exposed from their situation to the force of
every rude wave, and who, notwithstanding, so often escape unhurt? How
do they rear their young? From whence collect their prey?”
A DESCRIPTION AND ARRANGEMENT OF MINUTE AND RARE SHELLS.[154]
[154] Being possessed of Mr. Jacob’s own corrected copy of the work,
to which he has annexed the trivial names, I am thereby enabled to
affix them to the several shells here enumerated.
SERPULA.
_THE WORM-SHELL._
SERPULA BICORNIS. Plate XIV. Fig. 2. S. bicornis ventricosa. The bellied
semilunar worm-shell.
The colour white, opake, and glossy. From Sandwich and Reculver, though
not common.
SERPULA PERFORATA. Fig. 3. S. bicornis umbilico perforato. The semilunar
perforated worm-shell.
The colour white, opake, and glossy. From Sandwich: very rare.
SERPULA LACTEA. Fig. 4. S. tenuis ovalis lævis. The thin, smooth,
egg-shaped worm-shell.
The colour pellucid, with milky veins. From Sandwich: not common.
SERPULA LAGENA SULCATA. Fig. 5. S. (lagena) striata sulcata rotunda. The
round striated and furrowed flask worm-shell.
The colour whitish, transparent, and glossy. From Sandwich, Reculver,
and Shepey: very rare.
SERPULA RETORTA. Fig. 6. S. (retorta) rotunda marginata cervice curvatim
exerto. The marginated retort worm-shell.
The colour white and opake. From Sandwich: not common.
SERPULA INCURVATA. Fig. 7. S. recta anfractibus tribus contiguis
regulariter involutis. The straight horn worm-shell, with three close
intorted spires at the tip.
The colour white, semitransparent. From Sandwich: rare.
This shell, though resembling the semilituus of Linnæus, p. 1163, No.
280, is not of the genus of Nautilus, having neither syphon in the
aperture, nor the internal concamerated structure.
DENTALE.
_THE TOOTH-SHELL._
DENTALIUM IMPERFORATUM. Fig. 8. D. apice imperforata transverse
striatum. The imperforated transversely striated tooth-shell.
The colour white and opake. From Sandwich: not very common.
PATELLA.
_THE LIMPET._
PATELLA ROTA. Fig. 9. P. plana orbiculata margine regulariter dentato.
The toothed-wheel limpet.
The colour white and opake. From Sandwich: extremely rare.
HELIX.
_THE DEPRESSED SNAIL._
HELIX CARINATA. Fig. 10. H. striata apertura compressa tribus
anfractibus carinata. The striated suboval-mouthed snail, of three
spires and a sharp edge.
The colour light brown pellucid. In a fresh water stream, near
Faversham.
HELIX SPINOSA. Fig. 11. H. subglobosa umbilicata ore subrotundo margine
spinoso. The roundish mouth deeply umbelicated snail with a thorny
margin.
The colour brown pellucid. From Bysing Wood, near Faversham: exceeding
rare.
HELIX RETICULATA. Fig. 12. H. unici anfractus subumbilicata apertura
rotunda marginata eleganter reticulata. The round mouthed reticulated
single spired slightly subumbilicated snail.
The colour white and pellucid. From Reculver: extremely rare.
HELIX STRIATA. Fig. 13. H. striata apertura subovali anfractibus
supradorsalibus. The oval mouthed striated snail with the spires
reflected on the back.
The colour greenish, white pellucid. From Sandwich: very rare.
TURBO.
_THE PRODUCED SNAIL._
TURBO RETICULATUS. Fig. 14. T. subumbilicatus quatuor anfractibus
reticulatis apertura subrotunda. The slightly umbilicated turbo with
four reticulated spires, and a roundish aperture.
The colour white and pellucid. From Seasalter: very rare.