on the same principle, there is a less degree of variation than in dogs. In the dog, which is of all species the most domesticated, the variation extends to the production of an additional toe, and corresponding metatarsal bone in the hind foot". And in the human species, in the individuals of which, from their varied intercourse and modes of living, the limits of variation may antecedently be expected to have the widest range, there are families having six fingers. In concluding this part of the subject, I would observe that the principle, which we have just now been examining, is of very great importance as the basis of a physiological argument with reference to the identity of the human species throughout the world. For, inasmuch as all the variations in colour, form, and size, of the different nations of mankind, come within the acknowledged limits of specific variation in the animal kingdom, we have hence satisfactory physiological proof that all the varieties of the human race may have proceeded from one common parent. Of the truth of the general position indeed, of which the human species is a particular instance, the work of Aristotle now under consideration is in itself a strong argument: for, notwithstanding the lapse of ages which has taken place since it was written, the description of many species is so accun Ann. du Mus. tom. xviii. p. 342. pl. 19. rate, as to leave no doubt of the identity of those described by Aristotle with those to which the description is applicable at the present day o. SECT. IV. On those Animal Forms called Monsters, or Lusus Naturæ. THE subject of the present section is naturally connected with that of the latter part of the preceding and, although the occasion neither requires nor would justify even a brief examination of the laws which regulate the formation of monsters, or lusus naturæ, as they are often called, especially as they have been lately illustrated by that ardent French physiologist Geoffroy St. • It can hardly escape observation, or fail to excite surprise, that in the work now under consideration, Aristotle usually contents himself with stating facts: he very rarely reasons on their final causes; thus omitting what Cuvier calls one of the most beautiful and useful points in natural history. The following are, I believe, the only instances in which he deviates from mere description. He observes, when speaking of fish, that a great proportion of the spawn of those animals is destroyed in various ways; and that if this were not the case the species would become too numerous. (Τὰ μὲν πολλὰ φὰ οἱ ἄρρενες ἀνακάπτουσι, τὰ δ ̓ ἀπόλλυται ἐν τῷ ὑγρῷ, ὅσα δ ̓ ἂν ἐκτέκωσιν εἰς τοὺς τόπους εἰς οὓς ἐκτίκτουσι, ταῦτα σώζεται· εἰ γὰρ πάντα ἐσώζετο, παμπληθὲς ἂν τὸ γένος ἦν ἑκάστων. p. 169.) On another occasion he observes, that though the spring is the general season for propagation, yet occasionally the rule is set aside; where, for instance, the preservation of the offspring is the result. ('Opuŋtikwtata pèv οὖν ὡς ἐπὶ τὸ πᾶν εἰπεῖν πρὸς τὴν ὀχείαν τὴν ἐαρινὴν ὥραν ἐστίν· οὐ μὴν τὰ πάντα γε ποιεῖται τὸν αὐτὸν καιρὸν τῆς ὀχείας, ἀλλὰ πρὸς τὴν ἐκτροφὴν τῶν τέκνων ἐν τοῖς καθήκουσι καιροίς. p. 181.) Hilaire; it will not be perhaps considered impertinent to make a few observations on those remarkable productions, considered with respect to one of the probable final causes of their existence. The term lusus naturæ is applied to those natural productions, which vary in any remarkable degree, with respect to form, colour, structure, size, &c. from the general character of the individuals of the same species. The term, literally taken, implies a sportive effort of the creative power of Nature; and for the purpose of general description there is no objection to this term, being, as it now is, familiarized by long continued use. But as we have no ground for supposing that nature, or, to use the more proper expression, that the providence of the Creator ever acts without some wise and beneficent purpose, we must consider the term in a philosophical point of view, as expressing an effect, of the natural cause of which we are ignorant. What, then, is the real character of those unusual productions which are denominated lusus naturæ, or monsters; or, in other words, for what end has Providence ordained that such productions should be formed and subjected to our observation? And here, as has been observed in another part of this treatise, it will be found, upon even a cursory examination, that in a lusus naturæ the character of the species, however obscured, is never lost. There is no ground, in short, for supposing that nature has ever produced such an individual as a chimera or centaur. And Lucretius's scepticism in this point is justified on truly philosophical principles; on the difference namely of the physical constitution of the horse and of man: the horse at the end of his third year being full-grown, while man is yet almost an infant; and the horse being decrepit in his twenty-fifth or thirtieth year, when man is in his full vigour P. In pursuing this investigation, it would be obvious to ask, what are the limits which separate a lusus naturæ from the ordinary individuals of the same species? and we shall soon find that these limits are, in the majority of instances, undefinable. If, indeed, in comparing the several organs, agreement with respect to number be the criterion, the limits are for the most part fixed. Thus the human hand so very generally consists of five fingers, that an instance of an individual having more or less than five fingers would be justly esteemed an instance of a lusus naturæ. But even number is not always an ac P Sed neque Centauri fuerunt, neque tempore in ullo Lib. V. 876-889. knowledged criterion; for, with respect to the teeth, though thirty-two is the usual number in the human subject, yet the instances of persons having only twenty-eight are so frequent, that we can scarcely class them as deviations from the common law. But if size, or colour, or form be made the criterion, we evidently cannot then fix the limits; for in all these points there is an endless variety in individuals of the same species: so that it might perhaps be truly asserted, that out of the countless myriads of human beings that inhabit the earth, nay even out of all that have existed since the creation, no two individuals would be found to resemble each other, exactly, in even any one of those points. And in this wonderful diversity the infinite power of the Deity is distinctly manifested; for, in the exercise of human skill, the most accomplished artist, as soon as he ceases to copy an actual individual, falls into that general similarity of outline by which we are enabled to ascertain his style upon the first view. If, in the pursuit of our inquiry, we appeal to the distribution of the internal organs of the body, we shall find, that though with respect to many the position is determinable with considerable precision, yet with respect to others, the smaller veins and arteries, for instance, the variation is endless. But-and this most highly Z |