tadpoles into water contained in a reservoir, from which the light was excluded. The tadpoles grew, but did not become frogs. He afterwards removed some of them into a situation to which the light had free access. These soon lost their tail and fins, and were converted into perfect frogs: but the rest, which were kept in the dark, still continued in the state of tadpoles. I have now endeavoured to explain the functions of absorption, of circulation, and respiration; the manner by which the chyle is taken up, and carried into the system; how it is converted in the lungs into blood; and how the blood is distributed to every part of the body. I have likewise pointed out how nearly the functions by which all these effects are produced in the animal frame, resemble those functions in the vegetable system by which the crude sap is absorbed from the earth; how it is changed in the leaves into cambium; and how the cambium is conveyed all over the plant. In the early part of my essay I remarked that every organised being is composed of solid and fluid parts. The solids consist of muscular, membranous, and nervous substance; the fluids consist of aqueous and other matter. In the animal frame, all the solid and fluid substances are produced from the blood; in plants, they are produced from the sap. Skin, fat, brain, muscle, membrane, saliva, tears, bile, and urine, are all eliminated from the blood; bark, wood, pith, pollen, oil, sugar, &c., are all eliminated from the sap. The process by which muscle is extracted from the blood, and that by which wood is extracted from the sap, are termed secretion. There are many substances existing in the blood, which, in consequence of their peculiar chemical qualities, are enabled to escape from the system by transuding through the sides of certain organs; this is considered as a species of secretion: but secretion is properly the separation of substances from the blood, which did not previously exist in this fluid. The organs by which it is performed, in the animal frame, consist of vesicles or hollow sacs. The glands, such as the liver, the pancreas, &c., are composed of a congeries of these vesicles; among which blood vessels and excretory ducts abundantly ramify. The secreting organs of vegetables are precisely similar to those of animals. They consist of hollow bodies; and these, when collected into clusters, constitute glands, which are as abundant in the vegetable as in the animal system. Various speculations have been offered with regard to the theory of secretion. Van Helmont and Willis ascribed the process to fermentation; Hunter, Blumenbach, Bichat, and Abernethy ascribed it to the agency of the vital principle; Descartes, Boerhaave, and Haller, to a mechanical process; Keill and Prout to chemical action; Home, Brodie, and Philip, to nervous influence. Dutrochet ascribes secretion to endosmose. Perhaps none of these hypotheses are free from objections; but that which is correct with regard to animal secretion, will be correct with regard to the secretions of vegetables. (To be continued.) ART. III. On the supposed Pouch under the Bill of the Rook. By "Nec aliud quicquam . . . quæritur, Phædrus. "Nothing further is sought than to correct the errors of men, and to sharpen their penetration." WE read in that faulty work, Rennie's Montagu's Ornitho logical Dictionary [p. 432.], that "the rook is furnished with a small pouch at the root of the tongue." If the carrion crow were as useful to man, as the rook is known to be; if the jay and the magpie had less to answer for, on the score of petty plunder; and if the jackdaw did not expose itself to persecu tion, by its prying and suspicious habits, they would all be allowed by man to range at large without molestation; and then the naturalist would have that opportunity of examining their economy, which at present is denied him. Amongst many peculiarities in these birds, scarcely known, or even noticed, he would observe that at a certain time of the year, and only then, they all have, at intervals, an appearance of a pouch under the bill, quite as well defined as that which is seen in the rook. The idea would then occur to him, that ornithologists have either said too much, in stating that the rook is furnished with a small pouch at the root of the tongue; or too little, in not telling us that the carrion crow, the jay, the magpie, and the jackdaw are supplied with a similar convenience. The real matter of fact is this, that naturalists err when they ascribe a pouch to the rook. Though at times there is an actual appearance of a pouch under the bill of the rook, and also under the bills of the other birds just enumerated, still, upon a close inspection, it will be seen that there is no pouch at all in any of them. The young of all birds, from the size of the thrush to that of the wren, are satisfied with a single worm at one feeding, or with two, at the most. Thus, in fields and gardens, we see an old bird catch an insect, and fly away immediately with it to the nest. But food of this scanty measure would not be enough for the larger kind of insectivorous birds. The progeny would undoubtedly require more at each feeding; and, add to this, supposing the bird only carried one insect at each turn, too much time would be lost in passing to and from the nest. To obviate this, as birds of the pie tribe have no power, in health, to eject food which has descended into the stomach (saving the indigestible remnants of aliment, which are thrown up in the form of pellets), they collect a considerable quantity of insects into their mouth, and they confine them there, without letting them go down. the throat. By this process, a rook is enabled to pick up a sufficient supply of food, some miles from the nest ; and when its mouth will hold no more insects, the bird takes flight, and carries them to its expecting brood. The carrion crow, the jay, the magpie, and the jackdaw do the same thing precisely. Now, the gathered insects, being prevented from descending into the stomach, and at the same time not being able to escape at the bill, must necessarily form a lump under the lower mandible, where the skin, in all birds, is admirably formed for distention. This lump is what has given rise to the notion amongst naturalists, that the rook is furnished with a pouch at the root of the tongue. If this pouch be allowed in the rook, then it must be admitted that all birds are furnished with a pouch; and it must also be admitted that our tars are furnished with a pouch betwixt the mouth and the ear, because, for convenience' sake, they stow away their quid in that quarter. It may be easily accounted for, why ornithologists make no mention of a pouch under the tongue of the jay, the jackdaw, the magpie, and the carrion crow, while they describe, with such plausibility a pouch at the root of the tongue of the rook. The reason is this, the rook, in general, is the friend of man, and, in the breeding season, he becomes so tame that he may be approached within a few yards. This gives you a fine opportunity of observing the lump under the bill, when the skin in that part is distended with a supply of food. Indeed, you can observe it at a considerable distance, either while the bird is on the ground, or when it is flying across you, on account of its white appearance, contrasted with the sable plumage. On the other hand, the carrion crow, the magpie, the jay, and even the jackdaw, are all birds of ruined character. Their misfortunes make them shy; and thus you are prevented from having much intercourse with them. The gardener and the henwife can never be brought to look upon them with the least appearance of kind feeling; while the VOL. V. No. 28. LL gamekeeper, that cholera morbus to the feathered race, foolishly imagines that he proves his attention to his master's interests, by producing a disgusting exhibition of impaled birds on the kennel walls. Nay, show me, if you can, a young squire, idling from college, who does not try to persuade the keeper that it is his bounden duty to exterminate all manner of owls, ravens, carrion crows, hawks, herons, magpies, jays, daws, woodpeckers, ringdoves, and such like vermin, from his father's estate. With this destroying force to contend with, in the shape of keeper, squire, and henwife, it is not to be wondered at that naturalists have so few opportunities of watching individuals of the pie tribe through the entire course of their incubation; which individuals, if persecution did not exist, would be seen, in the breeding season, perpetually passing to and fro, with their mouths full of food for their young. In my little peaceful valley, where the report of the keeper's gun is never heard, and where the birds are safe from the depredations of man, the ornithologist has free access to pursue his favourite study. Towards the middle of May, he can see here the carrion crow, the jay, the magpie, and the jackdaw, filling their mouths with grubs and worms, the weight of which forces the pliant skin under the bill into the shape of a little round ball, just of the same appearance as that which is observed in the rook, with this trifling difference, that the lump is feathered in the first, and bare of feathers in the last. While I am writing this, there may be seen here a wild duck hatching her eggs in a nest upon a sloping wooded bank; while a carrion crow is hatching hers in a fir tree ten yards from the spot, and a windhover hawk is performing the same function in a fir tree about six yards on the other side of the duck. Forty yards from where the carrion crow is hatching, may be seen a barn owl sitting on her eggs in the hollow of an oak tree; and, at twenty yards' distance from the windhover, another white or barn owl has formed her nest in the decayed recesses of a tremendous oak. Though all these families keep the peace, I do not wish it to be understood that they are upon visiting terms. In another part, a long-eared owl is rearing her young in the last year's nest of a carrion crow. When the parent bird is asleep, you can see very distinctly the erect feathers on the head: but the moment she gets a sight of you, down go the erect feathers, and lie close to the head; so that an inexperienced observer might take the bird to be a tawny owl. This year, a wild duck has chosen her place of incubation twelve feet from the ground, in an oak tree, near the water; while, in the immediate vicinity, several magpies are hatching in undisturbed repose. I am sometimes questioned by country gentlemen (who have a keen eye for jugged hare and roasted partridges) on the propriety of befriending, what they consider, feathered vermin. I tell them that Professor Rennie has remarked, in this Magazine (Vol. V. p. 102.), “ that I have hitherto published nothing, respecting the economy or faculties of animals, of the least use to natural history." This being the case, I am trying to make up my deficiency in pen and ink, by establishing a sylvan enclosure, which any ornithologist is allowed to enter; and where he will have an opportunity of correcting, by actual observation, some of those errors which appear in the second edition of Montagu, by James Rennie, A.M. A.L.S. Moreover, sometimes, in a jocose kind of a way, I tell them I like to have all kinds of birds around me; and that I cannot find in my heart to kill a poor jay for sucking an egg, when I know "That I myself, carnivorous sinner, Walton Hall, May 9. 1832. CHARLES WATERTON. ART. IV. On the Preservation of Egg-shells for Cabinets of Natural History. By CHARLES WATERTON, Esq. "Si sumas ovum, molle sit, atque novum.” Schola Salernitana. I HAVE been blundering at this work for some years; "seeking for something I could not find," and always dissatisfied with myself on account of the failure. The object of my search was, to try to find out how I could properly dispose of the thin white membrane next the shell of the egg. When left in, it is apt to corrupt; in which case, the colour of the shell will sometimes fade, and an offensive smell is produced, which a lapse of years will not subdue. Last spring, I thought I had succeeded; but it turned out to be a very partial success. I, first, by blowing, discharged the contents of five swans' eggs, and then immersed the shells in a tub of water for a month. This enabled me to pull out the thin membrane, by means of a piece of wire bent at the end. But I found that the colour of the shell had faded considerably. Moreover, the process required too much time; and I saw that there would be great difficulty in doing small eggs. About three weeks ago, a bright thought (a rara avis with me) struck me, just as I was in the act of climbing up to a |