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All the changes in Ovid's Metamorphoses might have been effected by these appetencies, if the theory were true: yet not an example, nor the pretence of an example, is of fered of a single change being known to have taken place. Nor is the order of generation obedient to the principle upon which this theory is built. The mammae o of the male have not vanished by inusitation; mec curtorum, per multa saccula, Judaeorum propagini deest praputium. It is easy to say, and it has been said, that the alterative process is too slow to be perceived; that it has been carried on through tracts, of immeasurable time; and that the present order of things is the result of a gradation, of which no human, record can trace the steps. It is easy to say this ; and yet it is still true, that the hypothesis remains destitute of evidence. . The analogies which have been alleged, are of the following kind: The bunch of a camel, is said to be no other than the effect of carrying burthens; a service in which the species is . . . * : * : G * :
* I confess myself totally at a loss to guess at the reason, cither final or efficient, for this part of the animal frame, uhless there be some foundation for an opinion, of which I draw the hint from a paper of Mr. Everard Home, (Phil. Transact. 1799, p. 2.) viz. that the mammae of the foetus may be formed, before the sex is determined.
has been employed from the most ancient times of the world. The first race, by the daily loading of the back, would probably find a small grumous tumour to be formed in the flesh of that part. The next progeny would bring this tumour into the world with them. The life to which they were destined, would increase it. The cause which first -generated the tubercle being continued, it would go on, through every succession, to augment its size, till it attained the form and the bulk under which it now appears. This may serve for one instance; another, and that also of the passive sort, is taken from certain species of birds. Birds of the crane kind, as the crane itself, the heron, bittern, stork, have, in general, their thighs bare of feathers. This privation is accounted for from the habit of wading in water, and from the effect of that element to check the growth of feathers upon these parts: in consequence of which, the health and vegetation of the feathers declined through each generation of the animal; the tender down, exposed to cold and wetness, became weak, and thin, and rare, till the deterioration ended in the result which we see, of absolute nakedness. I will mention a third instance, because it is drawn from an active habit, as the two last were from passive habits; and that is the pouch of the pelican. The description which naturalists give of this organ, is as follows: “From the lower edges of the underchap, hangs a bag, reaching from the whole length of the bill to the neck, which is said to be capable of containing fifteen quarts of water. This bag, the bird has a power of wrinkling up into the hollow of the underchap. When the bag is empty it is not seen: but when the bird has fished with success, it is incredible to what an extent it is often dilated. The first thing the pelican does in fishing, is to fill the bag; and then it returns to digest its burthen at leisure. The bird preys upon the large fishes, and hides them by dozens in its pouch. When the bill is opened to its widest extent, a person may run his head into the bird's mouth; and conceal it in this monstrous pouch, thus adapted for very singular purposes”.” Now this extraordinary conformation is nothing more, say our philosophers, than the result of habit; not of the habit or effort of a single pelican, or of a single race of pelicans, but of a habit perpetuated through a long series of generations. The pelican soon found the conveniency of reserving in its mouth, when - * Goldsmith, vol. i. p. 32.
its appetite was glutted, the remainder of its prey, which is fish. The fulness produced by this attempt, of course stretched the skin which lies between the under-chaps, as being the most yielding part of the mouth. Every distension increased the cavity. The original bird, and many generations which succeeded him, might find difficulty enough in making the pouch answer this purpose: but future pelicans, entering upon life with a pouch derived from their progenitors, of considerable capacity, would more readily accelerate its advance to perfection, by frequently. pressing down the sac with the weight of fish which it might now be made to contain. These, or of this kind, are the analogies relied upon. Now, in the first place, the instances themselves are unauthenticated by testimony; and, in theory, to say the least of them, open to great objections. Who ever read of camels without bunches, or with bunches less than those with which they are at present usually formed? A bunch, not unlike the camel's, is found between the shoulders of the buffalo; of the origin of which it is impossible to give the account here given. In the second example; Why should the application of water, which appears to promote and thicken the growth of feathers upon the
bodies and breasts of geese, and swans, and other water-fowls, have divested of this covering the thighs of cranes? The third instance, which appears to me as plausible as any that can be produced, has this against it, that it is a singularity restricted to the species; whereas, if it had its commencement in the cause and manner which have been assigned, the like conformation might be expected to take place in other birds, which fed upon fish. How comes it to pass, that the pelican alone was the inventress, and her descendants the only inheritors of this curious resource? But it is the less necessary to controvert the instances themselves as it is a straining of analogy beyond all limits of reason and credibility, to assert that birds, and beasts, and fish, with all their variety and complexity of organization, have been brought into their forms, and distinguished into their several kinds and natures, by the same process (even if that process could be demonstrated, or had it ever been actually noticed) as might seem to serve for the gradual generation of a camel's bunch, or a pelican's pouch. The solution, when applied to the works of nature generally, is contradicted by many of the phaenomena, and totally inadequate to others. The ligaments or strictures, by