INADEQUACY OF NATURAL SELECTION, ETC. 617 



creatures have diverged in the proportions of their limbs in 

 opposite directions ? Take, again, the articulate animals. Com- 

 pare one of the lower types, with its rows of almost equal-sized 

 limbs, and one of the higher types, as a crab or a lobster, w4th 

 limbs some very small and some very large. How came this 

 contrast to arise in the course of evolution, if there was the equality 

 of variation supposed ? 



But now let us narrow the meaning of the phrase still further, 

 giving it a more favourable interpretation. Instead of con- 

 sidering separate limbs as co-operative, let us consider the com- 

 ponent parts of the same limb as co-operative, and ask what 

 would result from varying together. It would in that case 

 happen that, though the fore and hind limbs of a mammal might 

 become different in their sizes, they would not become different 

 in their structures. If so, how have there arisen the unlikenesscs 

 between the hind legs of the kangaroo and those of the elephant ? 

 Or if this comparison is objected to, because the creatures belong 

 to the widely different divisions of implacental and placental 

 mammals, take the cases of the rabbit and the elephant, both 

 belonging to the last division. On the hypothesis of evolution 

 these are both derived from the same original form ; but the pro- 

 portions of the parts have become so widely unlike that the 

 corresponding joints are scarcely recognized as such by the un- 

 observant : at what seem corresponding places the legs bend in 

 opposite ways. Equally marked, or more marked, is the parallel 

 fact among the Articulata. Take that limb of the lobster which 

 bears the claw and compare it with the corresponding limb in an 

 inferior articulate animal, or the corresponding limb of its near 

 ally, the rock lobster, and it becomes obvious that the component 

 segments of the limb have come to bear to one another in the 

 one case, proportions immensely different from those they bear 

 in the other case. Undeniably, then, on contemplating the 

 general facts of organic structure, we see that the concomitant 

 variations in the parts of limbs, have not been of a kind to pro- 

 duce equal amounts of change in them, but quite the opposite 

 — have been everywhere producing inequalities. Moreover, we 

 are reminded that this production of inequalities among co-opera- 

 tive parts, is an essential principle of development. Had it not 

 been so, there could not have been that progress from homoge- 

 neity of structure to heterogeneity of structure which constitutes 

 evolution. 



We pass now to the second supposition : — that the variations 

 in co-operative parts occur irregularly, or in such independent 

 ways that they bear no definite relations to one another — miscel- 

 laneously, let us say. This is the supposition which best corre- 

 sponds with the facts. Glances at the faces around yield 



