Part 49

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.

TURBO EBURNEUS. Fig. 15. T. quinque anfractibus ventricosis apertura subrotunda. The five spired ventricose turbo with a roundish mouth.

The colour white and opake. From Reculver: very rare.

TURBO STRIGATUS. Fig. 16. T. tribus anfractibus primo strigis tribus transversis apertura subovata. The three spired turbo, the first spire with three transverse ridges and a suboval aperture.

The colour opake white. From Seasalter: very rare.

TURBO ALBIDUS. Fig. 17. T. turritus septem anfractibus strigatis apertura ovali. The taper turbo with seven ridged spires and an oval aperture.

The colour opake white. From Sandwich: rare.

TURBO CARINATULUS. Fig. 18. T. turritus carinatus septem anfractibus apertura coarctata marginata. The taper carinated turbo with seven spires and a contracted marginated aperture.

The colour opake white. From Sandwich: very rare.

TURBO CLATHRATULUS. Fig. 19. T. clathratus sex anfractibus apertura ovali marginata. The barred six spired turbo with an oval marginated aperture.

The colour opake white. From Sandwich: exceeding rare.

TURBO CRASSUS. Fig. 20. T. crassus clathratus quinque anfractibus apertura rotunda marginata. The thick barred turbo of five spires and a round marginated aperture.

The colour opake white. From Sandwich: very rare.

TURBO PUNCTATUS. Fig. 21. T. turritus perversus novem anfractibus punctatis apertura coarctata. The reversed taper turbo of nine dotted spires and straitened aperture.

The colour light-brown opake. From Sandwich: not common.

TURBO SHEPEIANUS. Fig. 22. T. sex anfractibus reticulatis apertura ovali submarginata. The six spired reticulated turbo with an oval submarginated aperture.

The colour semipellucid white. From Shepey island: very rare.

TURBO SANDVICENSIS. Fig. 23. T. tribus anfractibus reticulatis apertura unidentata. The three spired elegantly reticulated turbo with a one toothed oval aperture.

The colour pellucid white. From Sandwich: exceeding rare.

TROCHUS.

_THE TOP-SHELL._

TROCHUS FUSCUS. Fig. 24. T. umbilicatus quinque anfractibus marginatus apertura subrotunda. The five spired umbilicated marginated top-shell with a roundish aperture.

The colour opake brown. From Sandwich: common.

BUCCINUM.

_THE WHILK._

BUCCINUM OBTUSULUM. Fig. 25. B. ampullaceum tribus anfractibus apertura ovali. The bellied whilk of three spires with an oval aperture.