off; hence it is found long after death in a state of rigidity and contortion, with the fins preternaturally erect.

DUSKY PERCH (PE'RCA L. ROBU'STA C.).

The fish (fig. 7.) from which my description was taken weighed sixteen pounds, and measured 3 ft. in length, and 7 in. in

depth, exclusive of the fins, the body thick and solid. Under jaw longest, both, as well as the palate, having numerous slender incurved teeth; in front of the under jaw was a bed of them. Lips like those of the codfish, two large open nasal orifices, and a large hole under the projection of the nasal bone. First plate of the gill covers serrate, the second with a broad flat spine projecting through the skin, and pointing backward; the fleshy covering of the gill covers elongated posteriorly; seven rays in the gill membrane. Body and head covered with large scales, lateral line gently curved. Dorsal fin single, long, expanding towards its termination, with eleven spinous rays, the first short, and seventeen soft rays, the two last from one origin. Pectoral fin round, nineteen rays; ventrals fastened down by a membrane through part of their course, six rays. Vent an inch and a half from the origin of the anal fin, which fin has two spinous and nine soft rays, the last two from one origin. Tail roundish, sixteen rays. Colour of the back reddish brown, lighter on the belly; two slightly marked lines on the gill covers running obliquely downward, one on each plate. The gill covers are not ridged. In its aspect this fish has some resemblance to the Làbri, yet it has none of the generic characters by which these fishes are distinguished. That it should be placed among the perches I make no question; but my most industrious search has not been able to find that it has been either figured or described: until, therefore, some other naturalist shall be more fortunate, I venture to denominate it P. robústa, from its great size and strength. I have never seen more than one specimen, which was taken with a line.

BURACO DE VELHA, Gen.?

This fish is 12 or 14 in. long, and 4 in. wide; from the head the back is elevated and arched; the head itself sharp, in each jaw a row of very small teeth. The lower part of the mouth and tongue a bright red, iris of the eye gold and dusky. A single dorsal fin, the first rays firm, the posterior flexile; tail forked; scales moderate, silvery, bluish from the head along the back; lateral line white. (Ray, Syn. Pisc., p. 134.)

I am uncertain whether this fish is rightly arranged among the Pércæ; and unfortunately I was prevented from examining a species that was taken at Looe a few years since, of which I received an account from that place. This is probably the only instance of its having ever visited the British seas.

SPANISH MACKAREL (SCO'MBER L. MACULATUS C.);
Class III. Thoracic Fishes.

This fish (fig. 8.) attains the weight of four or five pounds; but the specimen described measured no more than 14 in. in

length, the figure round and plump, 6 in. in compass near the pectoral fins, the thickness of its figure being carried far towards the tail. Mouth large, jaws of equal length, teeth small, tongue movable and pointed. Head large and long; eye large, 1 in. from the snout, and itself in. wide; from the snout to the pectoral fin 3 in. Rays of the gill membrane six, concealed. Lateral line at first slightly descending, then straight. Scales on the superior plate of the gill covers, as well as on the body. First dorsal fin in a chink, seven rays, the first shorter, second and third of equal lengths; spurious fins six above and below, the anterior not high; tail divided, and at its origin doubly carinated. Vent prominent. Colour dark blue on the back, striped like the mackarel, but more obscurely and with fewer stripes; a row of large dark spots from the pectoral fin to the tail, sides and belly thickly covered with smaller dusky spots. The tail, gill covers and sides, and behind the eye, bright yellow. From the mackarel, which it resembles, this fish differs in the markings of the head, longer snout, larger eye and gape, longer head, and in

having scales on the anterior gill covers. The body is not nearly so much attenuated posteriorly; the ventral fins are sharp and slender, those of the mackarel wider and more blunt in the former, the pectorals lie close to the body; in the latter, they stand off; in the latter, also, is a large angular plate, the point directed backward, close above the pectoral fins, which does not exist in the Spanish mackarel (S. maculàtus C.).

It seems to be the Còlias Rondelètii of Ray. (Syn. Pisc., p. 59.) I have given it the name by which it is known to our fishermen.

This fish is scarce, but some are taken every year. It does not often take a bait, although the fishermen inform me that this sometimes happens; and that its infrequency is owing to the difference of feeding rather than to want of rapacity. It is more frequently taken in drift nets; but even then it is only one at a time, and at considerable intervals. It is in no estimation as food.

MUD LAMPREY (PETROMY ZON L. CE CUS Ray); Class VI. Chondropterygous Fishes.

This species (figs. 9, 10.) grows to the length of 6 in., and is about the size of a goose-quill. The mouth, when open, is

10

irregularly oval, throat capacious, teeth large and blunt, placed circularly from the roof of the mouth to the under jaw; upper lip prominent, fleshy, movable at the sides. Orifice on the head; apertures for breathing along the sides, seven in number. The body dilated at this part. No eye discoverable. Body cylindrical to the vent, which is far back, thence compressed, tapering. First dorsal fin on the hind part of the back, small and narrow; the second close to it, elevated, and then narrow, passing round the extremity of the body, and below reaching half-way from the tail to the vent. Colour a dusky yellow, dark on the back, light below; fins light.

This species, from the absence of eyes, is sufficiently distinguished from others of its genus. It is mentioned by Ray (Syn. Pisc., p. 35.), but omitted in later systems of natural history.

If in its habits the silver lamprey (P. fluviatilis L.) bears a resemblance to the glutton (Ursus gùlo L.), this makes as near an approach to the mole (Tálpa europæ'a L.). It frequents our smaller streams, living in the muddy bottom, from which it rarely, if ever, willingly emerges. I have kept it for months in stagnant water, with mud at the bottom, without injury to its health or activity. The only apparent use of its fins is to enable it to regain its station, when forced from it by violent torrents. When kept in clear water it seems to sleep much. I have never found this species to attach itself to any object by the mouth; but the lips are capable of extensive and complicated motions. It spawns at the end of April and the beginning of May. Fishermen collect them to use as bait when whiffing for pollacks.

ART. V. An Essay on the Analogy between the Structure and Functions of Vegetables and Animals. By WILLIAM GORDON, Esq. Surgeon, Welton, near Hull. Read before the Hull Literary and Philosophical Society, Nov. 19. 1830. Communicated by Mr. GORDON.

(Continued from Vol. IV. p. 393.)

I HAVE now pointed out the close analogy that exists between vegetables and animals, in so far as it regards the form of their ultimate corpuscles, the composition, and extensive diffusion of their membranous matter, the structure of their cellular tissue, and the organisation and functions of their cutaneous system. I shall next endeavour to show that plants, as well as animal beings, possess a muscular tissue. In order to do this, I must first take a review of the properties of muscular fibre, as they are exhibited in the animal body.

The properties of muscle may be divided into physical and vital. The former are, cohesion, flexibility, extensibility, and elasticity. On these it is not necessary for me to make any observations. The vital property of muscle is what more immediately concerns our subject, and is termed contractility: it is that specific faculty which muscular fibre possesses of contracting or shortening itself. When a stimulant is applied to a muscle, its fibres are thrown into what is called a state of contraction: its belly swells out, and grows hard to the touch; its surface, which in its natural condition was smooth, becomes

wrinkled, and its two extremities approximate, so that the parts to which they are attached are drawn nearer together: thus, when the biceps flexor muscle is made to contract, the. forearm and hand are raised towards the shoulder. Contractility, or, as it is called by some, irritability, is peculiar to muscular fibre, and does not belong to any other animal solid whatever. Blumenbach has, indeed, ascribed to membrane a. kind of contractile power; but the example of it which he adduces can, with more propriety, be referred to elasticity.. Muscular contraction never takes place, except on the application to the muscular fibre of some irritating agent, which is called a stimulus. These agents or stimuli are exceedingly numerous, and consist of mechanical impulses of every degree, of a variety of chemical substances, of electricity, and of volition. The older physiologists endeavoured to account for contractility on mechanical principles, and to refer it to the operation of elasticity; but, if we carefully note the phenomena that attend it, we shall perceive that it bears no analogy what-, ever to this or any other species of mechanical force.

In the first place, the contraction of a muscle is always greater than the cause by which it is produced: so that it appears that in contractility there is an actual generation of power; whereas, in the reaction of elastic bodies, the effect. produced can never exceed the amount of the cause producing it. In the second place, in contractility, the reaction commences during the application of the mechanical agent; but in elasticity, the reaction cannot take place until the force that had been impressed is removed. For example, if a straight piece of whalebone be bent into a curve, it cannot regain its original form until one of its extremities be liberated; but, if the surface of a muscle be scratched with a sharp-pointed instrument, its fibres begin to contract the very moment the operation is commenced. In the third place, the contraction of muscular fibres, after continuing some time, is succeeded by a state of relaxation or exhaustion, even although the stimulus continues to be applied to them; and muscles which have become exhausted or relaxed, after having been in a state of contractility, cannot be again excited to act until a certain period has elapsed. In mechanics, there is nothing which bears the slightest resemblance to this; for in every description of machinery a certain effect will always be produced so long as the application of an efficient cause is continued. Such are the properties of muscular fibre, and such are the phenomena attendant upon and peculiar to contractility.

We shall now proceed to examine some of the actions of vegetable organs. If we can discover that these actions are accompanied with phenomena such as we know can only be