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the lining of the tubes in the quadruped is not nerve, but a kind of internal periosteum.

"Fishes thus evidently possessing the organ of hearing, precludes the necessity of making any experiment, which only leads to prove this fact. One trial will however be related, to shew that Sound affects them, and is one of their Guards, as it is in other Animals.

"When in Portugal, in 1762," says Mr. H. "I observed in a Nobleman's garden near Lisbon, a small fish-pond full of different sorts of fish. Its bottom was level with the ground, and was made by forming a bank all around, with a Shrubbery close, to it; whilst lying on the bank seeing the fish, I desired a Gentleman, who was my companion, to go behind the Shrubs (that there might be no reflection of light from the flash) and fire his Gun. The moment the report was made, the fish seemed to be uniformly affected, for they vanished immediately, raising as it were a cloud of mud from the bottom. In about five minutes afterwards, they be gan to appear, and again swam about as before."

Mr. HUNTER allows, that although GEOFFROI, who wrote upon this topic, cannot be said to have given a perfect account of the Organ of hearing in fishes, yet he should be considered as a discoverer ; and with modesty Mr. H. continues, that he should not have claimed a discovery, to which Mr. GEOFFROI had a prior right, had he been acquainted with that Author's researches and pretensions. The Hearing of fishes has been long and strongly con tended, but by the skilful investigation of our cele

brated Anatomist, the Question of the fishes Hearing seems to be decided.

The Sight of fishes is perhaps the most perfect of all their Senses, and yet their seeing is far inferior to that of most other animals; the Eye in almost all fish is covered with the same transparent skin that surrounds the rest of the head, and which probably defends it in the water, as they are without eye-lids; the globe is more depressed in front, and is furnished behind with a muscle, which serves to lengthen or flatten it according to the animal's necessities. The chrystalline humour, which in Quadrupeds is flat, and of the shape of a button-mould, in fishes is round as a pea, or sometimes oblong like an egg. A general idea of this may be formed from the glasses used by near-sighted people: those whose chrystalline humour is too convex, or in other words, too round, are always very near-sighted, and have recourse to concave glasses to amend this imperfection of Nature. The chrystalline humour of fish is so round, that it is not in the power of glasses, much less of water, to correct their Vision. This humour in fishes is that hard pea-like substance which is found in their eyes after boiling; in the natural state, it is transparent, and not much harder than a jelly. There is no evidence of any fishes seeing at a considerable distance, and the conduct of many of them, that are deceived by the different baits prepared in imitation of their food, gives room to suspect, that Objects are not very distinctly perceived by them, even when near.

The Iris also in the Eyes of Fish does not admit

of Contraction. This is a great difference, of which the probable reason is, that the diminished light in Water is never too strong for the Retina.

In the Eel, which has to work its head through sand and gravel, the roughest and hardest substances, there is placed before the Eye, and at some distance from it, a transparent, horny, convex case, or covering, which, without obtruding the sight, defends the Organ. To such an Animal, could any thing be more wanted or more useful?-Thus, in comparing together the Eyes of different kinds of Animals, we see in their resemblances and distinction one general plan laid down, and that plan varied with the varying Exigencies to which it is applied. There is one property, however, common to all Eyes, at least to all which have been examined*, namely, that the Optic Nerve enters the bottom of the Eye, not in the Centre or Middle, but a little on one side; not in the point where the Axis of the Eye meets the Retina, but between that point and the Nose. The difference which this makes, is, that no part of an Object is unperceived by both Eyes at the same time.

In all animals, Respiration, or the admission of Air into the body, seems necessary to the support of life in the spinous fishes, which are more immediately the objects within our notice, respiration is performed by the gills, without the cavity of the body; but the precise manner in which this operation is carried on, is one of those Secrets of Nature,

*The Eye of the Seal or Sea-calf is said to be an Exception.

which neither the glasses nor the knife of the Anatomist have ever yet been able to develope. Those who have seen a fish in water, will recollect the motion of its Lips and Gills, or at least of the bones on each side that cover them; in the animal, this motion is doubtless analogous to our breathing, but it is not air, but water, that the fish actually sucks in and spouts out through the gills at every motion, while the bony covering of the gills prevents it from going through them until the animal has drawn the proper quantity of Air from the body of Water there imprisoned, the bony covers then open, and give it a free passage; the gills, by this means, are again opened, and a fresh quantity of water is admitted. Should the fish be obstructed in the free play of its gills, or the bony covers, by a string tied round them, be kept from moving, the Animal would speedily be convulsed, and die in a few minutes. The manner indeed whereby the Air is transmitted from the lungs of quadrupeds into the blood, is perhaps equally mysterious as its passage from the gills of fishes into the arteries leading to the heart. As the Air and Water pass quickly through the Gills, without any apparent effort to separate them, probably but a small quantity of the former is absorbed, but that by the frequent transition of the water, a sufficiency of it may be admitted to supply animals whose blood is not in a great abundance, and is naturally cold.

But however small a quantity of Air may suffice to sustain the life of a fish, some portion is absolutely essential to every living being: the Death of fish in a severe frost is in consequence of the congelation

of the surface, whereby the external Air is excluded; the animals below must of course perish; and the eagerness to procure a supply of Air is manifested, by the suffocating fish instantly crowding to any Aperture made in the Ice, where to obtain it they will suffer themselves to be caught by the Hand.

Next to the necessity of breathing Air, that of devouring food seems to be the most urgent and constant in the constitution of fishes. Among them, both in Strength and Avidity, this Appetite surpasses those boundaries, which, in the other orders of the Animal World, Nature seems to have prescribed. Every aquatic animal that has life, falls a victim to the indiscriminate voracity of one or other of the fishes. Insects, worms, or the spawn of other Tenants of the Waters, sustain the smaller tribes, which in their turn, are pursued by millions larger and more rapacious. A few feed upon mud, aquatic plants, or grains of corn, but the far greater numbers subsist upon animal food alone, and of this they are so ravenous, as to spare not those of their own Kind. That there are vegetables in both fresh and salt waters admits no doubt, and these may furnish food to particular fishes; but those sorts are few, perhaps no one kind can be pointed out, that subsists entirely upon them; and although most fishes eat flies and terrestrial worms when they come in their way, yet in the immeasurable 'waste of Waters surrounding this Globe, the Swarms of fishes are so immense, that the subsistence to be derived from the above sources appears to be altogether disproportioned to their wants, and those of a smaller size seem to constitute

VOL. II.

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