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Few things, perhaps, show more vividly Aristotle's scientific instincts in natural history than his appreciation of the real character and relations of the aberrant forms of animals. We have, in the passage already quoted, seen how he appreciates the bat as a quadruped: he has elsewhere (Nat. Hist. lib. vi. c. 11) described with accuracy the position of the whales as mammiferous and viviparous animals, and as breathing air like ordinary quadrupeds. The notices which he has given of the seal are still more curious and interesting; he not only has given a particular and, we believe, correct sketch of its habits (ibid. lib. vi. c. 11), but he shows in one passage how the fins are the homologues of the feet of ordinary quadrupeds; although, as he remarks, the hinder ones assume a form very similar to the tail in the fishes (ibid. lib. ii. c. 1). In another passage (ibid. c. 3) he adduces the character of its teeth as an evidence of its being an animal closely connected with the fishes; in another he accounts for the absence of an external ear possessed by ordinary quadrupeds, on the ground that the purpose of such an ear being to collect the movements of the air, it would be useless to an animal living, not in the air, but the water (De Gen. An. lib. v. c. 2).
In this point of view, his discussion of the relations of the ostrich, the most quadruped-like of all birds, is very curious :
"The African ostrich," he says, “bas the organs in part of a bird, in part of a quadruped. For, inasmuch as it is not a quadruped, it has wings; and inasmuch as it is not a bird, it does not fly in the air, and its wings are useless for flight and covered with hair. Moreover, inasmuch as it is a quadruped, it has upper eyelashes, and the parts about the head and the upper parts of the neck are bare, so that its eyelashes appear more hairy ; inasmuch as it is a bird, its lower parts are covered with feathers, and it has two feet like a bird, but cloven-hoofed like a
mory' and 'recollection' as equivalents to the uvhun and dvduvnois of the Greeks respectively, has never, we think, gained any firm foothold in our language or thoughts. But the passage from Fuller shows that it was not unknown to our elder writers ; and so in Spenser it has given rise to the distinct impersonations of the old man Eumnestes and the boy Anamnestes, who tends him (Faerie Queene, book ii, canto 9):
“ His chamber all was hanged about with roles
And old records from ancient times derived,
Some made in books, some in long parchment scroles,
Amidst them all he in a chair was set,
Therefore he Anamnestes cleped is,
quadruped, for it has not claws, but hoofs. The reason of this is, that its size is that not of a bird but of a quadruped. For, generally speak
, ing, it is necessary that the size of birds should be very small ; for it is not easy for a body of great mass to be moved through the air" (De Part. Anim. lib. iv. c. 13). Allowing for a little exaggeration in the statement that this bird is cloven-hoofed, this account is substantially accurate; and it is curious to find Cuvier, in his Règne Animal, reproducing, not only several of the statements in a not dissimilar form, but giving the like reason with Aristotle for the ostrich's incapacity to fly.
By the side of that anatomy which takes cognisance of the final causes of the different animal forms, there has sprung up, and at length reached a definite development, another anatomy, which has to do with the forms of animal life, as abstracted from all consideration of the ends to which they are applied,—that science which is known as morphology. This latter science has grown up as it were by necessity, because it has been found that the law of final causes will not account for all the facts that need accounting for, and that under all reasonings from final causes there lies an assumption, for a long while understood, and now at length expressed, of a community or identity of form, except so far as varied by the diverse final causes. Thus, for example, if I find a single bone of some extinct quadruped, and find certain differences between it and its nearest known ally, which involve a difference of food or habitat, or mode of life, 1 shall conclude that there were certain differences in form corresponding with these differences of food, or habitat, or life; but, except to that extent, the animal I should reconstruct would be alike in form. Such reasoning is found by experience to be sound ; and whilst at first sight it may appear to proceed on the purposes of the animal structure alone, it does in fact involve and assume another principle, namely, that of a community of form, or type, irrespective of the identity of end. And this munity of type we every where find throughout nature: we find it first running throughout all the members of the different kingdoms of nature, and secondly, running through all the different parts of the same animal or plant. Thus, for example, we find all the infinite variety of the forms of the flowers of phanerogamous plants developed out of a few simple forms, the stamens, the petals, and so forth; and we find, again, that all the parts of every plant are but modifications of one and the same simple part, namely, the leaf; and the same might easily be illustrated with regard to quadrupeds and the vertebra, as the simplest element of their structure. But we should be wandering too far from our purpose into this most inviting part of natural his
tory, which seeks out, amidst the varying phenomena the ideals of nature, the creative thoughts of the Creator,-if we may so dare to say; which makes one feel that in the plan of nature order and beauty stand far above even its own glorious and unselfish utilitarianism.
Did Aristotle know any thing about this part of natural history? We answer that the homologies of the different parts of the human frame did not entirely escape his observation ; and in the 11th chapter of the first book of his History of Animals he has some curious observations on the relations of its parts, comparing the upper and the lower, the fore and the hind, and the right and the left, respectively. But into the higher law of morphology, that which depends on a recognition of form as distinct from the end, he had no insight. This is strange, when we consider that no treatment of natural history was perhaps ever so well suited to bring out the exact issue raised by morphology as that which Aristotle pursued. In the Physics (lib. ii. c. 3) he had already laid down and defined the four kinds of causes which are to be inquired into. These are, as every one knows, first the material cause, as in the case of a statue, the brass; secondly, the formal cause, the idea and exemplar in the mind of the craftsman ; thirdly, the efficient cause, as the craftsman himself; and lastly, the final cause, the end and object for which the statue was wrought.
Now it is upon this classification of causes that Aristotle has mapped out his discussions on natural history; and it will be at once seen that such a division of the subject necessarily discriminates between the two branches of anatomy,—the teleological and the morphological,—that which has to do with the final, and that which has to do with the formal causes. The actual form of any given animal is, so to speak, the diagonal between these two causes; and thus the mode of discussion proposed by Aristotle invited almost of necessity an attempt to resolve the diagonal into its component forces. Moreover, Plato's doctrine of ideas had raised the same question, though in a yet more transcendental form; so that the existence or non-existence of morphology came inevitably before Aristotle. But, as we have seen, he never attained to any conception of the law of form in the animal structure; and in a passage in which the four causes are recapitulated by him in their application to zoology, he affirms shortly, and without any reason given, that the formal and final causes are in this case one and the same, thus negativing the existence of the science in question.
It would be unreasonable and absurd to blame Aristotle for not grasping the principle of morphological anatomy; but if any defence were needed, it might be found in this, that he did not then know whether teleological reasonings alone were sufficient or insufficient to answer all the problems presented by the forms of animals; and until he knew that they were insufficient, he had no need to resort to any other principle. For, in fact, morphology has been discovered because teleology has been found insufficient, and has left a residual phenomenon which morphology
* De Generat. Anim. lib. i. c. 1.
а alone can account for. Indeed, it must be admitted that as we can perhaps never feel sure that we know exhaustively all the purposes of a creature, or all the relations of organs to their purposes, the doctrine of morphology lies open to the objection of being supported only by arguments from our ignorance; so that with the knowledge of Aristotle, it would perhaps have been rash rather than praiseworthy to have invoked into the explanation of animal forms any other principle than that of final causes.
He who compares the natural history of the moderns with that of the ancients, even in its most scientific development, will of course be struck with the vast advance made in the collection and comparison of facts, the correction of errors, and the improvement of the means and method of observation. But he will be struck too with another thought, which it will be well for him also to ponder, - we mean, that almost all the great ultimate questions which presented themselves to the ancients present themselves to us also in nearly the same form, and with nearly the same difficulties attending their solution.
Thus, for instance, the great question about the development of animal life and form, how far the need has gone before and caused the development, or the development has preceded and owed its origin to design,—the question, we mean, which has of late years been popularly raised by the Vestiges of Creation,was familiar to the ancient naturalists; and there were among them, as among us, two parties, the one for and the other against what we may call the development theory. Thus Aristotle (De Partibus An. lib. i. c. 1) says that the first natural philosophers held,“ that from water running into the body the stomach arose, and all the organs devoted to the reception of food; and that by the passage of the breath the nostrils were rent open.” From this view he expresses his dissent, and sums up his conception of the matter in the very Aristotelian remark, " that birth is for the sake of being, and not being for the sake of birth.” But the debate still survived, and reappears amongst the Roman naturalists. Lucretius has discussed the subject, in a way which might at first sight be confounded with the views of the Stagyrite, because he does not put the use before, but after, the creation of the organ; but the motive with which this is done is essentially
different, because Lucretius conceives the organ to have preceded the use, not by design and with a view to the use, but by accident only, the use being a thing purely casual:
“ Nil ideo quoniam natum est in corpore, ut uti
Possemus; sed quod natum est, id procreat usum.
Lib. iv. 835-843. The modern doctrine of development tells us, as has been often said, that we are only fishes in a higher stage, and that we each have been a fish ourselves. Now Plutarch has a story which forcibly recalls this statement of the modern doctrine ; for he tells us that Anaximander taught that mankind were originally born of fishes; and that when they had been nourished up and became able to help themselves,-reached a proper stage of development, to use more modern language,-they were then cast forth, and took to the land; and that for this reason the philosopher affirmed fishes to be the father and mother of mankind, and on that ground forbade the eating of them. We wonder whether it would be possible to discover the secret author of the Vestiges by a general invitation of all the savans of the country to a white-bait dinner.
The spontaneous generation of animals is another of those ultimate questions in natural science of which we have spoken. Every schoolboy, at least of the type with which Lord Macaulay was familiar, remembers the recipe which Virgil gives in the fourth Georgic for the production of bees where the hive may have lost its usual colony, whereby a brood of insects is raised from the blood of the slaughtered heifer :
“ Interea teneris tepefactus in ossibus humor
Æstuat : et visenda modis animalia miris,
Georgics, iv. 308. It is impossible to read these lines and not to recall the acari which Mr. Crosse saw, or thought he saw, developing on the stone in his galvanic battery; and the question raised by the two narratives is identically the same. If one may judge from rather a brief passage in his Treatise on the Soul (lib. ii. c. 4, § 2), Aristotle did not deny the possibility of spontaneous genera
* Plutarch, Conviv. Disput. lib. viii. quest. 8, § 4, edit. Wytt.