242 THE ORlOiy OF SPECIES 



animals are used for as widely different purposes as it is 

 possible 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 conclusion: "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 relationship, of inheritance 

 from a common ancestor?" 



Geoffrey St.-Hilaire has strongly insisted on the high 

 importance of relative position or connection in homol- 

 ogous 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 forearm, 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 different than the immensely 

 long spiral proboscis of a sphinx-moth, the curious folded 

 one of a bee or bug, 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 maxillee. 

 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 ex- 

 plain this similarity of pattern in members of the same 

 class, by utility or by the doctrine of final causes. The 



