Page - 473 - in The Origin of Species

MORPHOLOGY 473 some other Australian marsupials,—should all be constructed on the same extraordinary type, namely with the bones of the second and third digits extremely slender and enveloped within the same skin, so that they appear like a single toe furnished with two claws. Notwithstanding this s'milarity of pattern, it is obvious that the hind feet of these several animals are used for as widely different purposes as it is pos- sible to conceive. The case is rendered all the more striking by the American opossums, which follow nearly the same habits of life as some of their Australian relatives, having feet constructed on the ordinary plan. Professor Flower, from whom these statements are taken, remarks in conclu- sion : '"We may call this conformity to type, without getting much nearer to an explanation of the phenomenon ;" and he then adds, "but is it not powerfully suggestive of true rela- tionship, of inheritance from a common ancestor?" Geoffroy St. Hilaire has strongly insisted on the high im- portance of relative position or connexion in homologous parts; they may differ to almost any extent in form and size, and yet remain connected together in the same invariable order. We never find, for instance, the bones of the arm and fore-arm, or of the thigh and leg, transposed. Hence the same names can be given to the homologous bones in widely different animals. We see the same great law in the construction of the mouths of insects: what can be more dif- ferent than the immensely long spiral proboscis of a sphinx- moth, the curious folded one of a bee or btig, and the great jaws of a beetle?—yet all these organs, serving for such widely different purposes, are formed by infinitely numerous modifications of an upper lip, mandibles, and two pairs of maxilla;. The same law governs the construction of the mouths and limbs of crustaceans. So it is with the flowers of plants. Nothing can be more hopeless than to attempt to explain this similarity of pattern in members of the same class, by utility or by the doctrine of final causes. The hopelessness of the attempt has been expressly admitted by Owen in his most interesting work on the 'Nature of Limbs.' On the ordinary view of the independent creation of each being, we can only say that so it is;—that it has pleased the Creator