424 DARWINISM chap. 



that sheep and goats are specially mountain and rock-loving 

 animals may be explained by their being a later modification, 

 since the divided hoof once formed is evidently well adapted 

 to secure a firm footing on rugged and precipitous ground, 

 although it could hardly have been first developed in such 

 localities. Mr. Cope thus concludes : " Certain it is that the 

 length of the bones in the feet of the ungulate orders has a 

 direct relation to the dryness of the ground they inhabit, and 

 the possibility of speed which their habit permits them or 

 necessarily imposes on them." 1 



If there is any truth in the explanation here briefly 

 summarised, it must entirely depend on the fact of individual 

 modifications thus produced being hereditary, and we yet 

 await the proof of this. In the meantime it is clear that the 

 very same results could have been brought about by variation 

 and natural selection. For the toes, like all other organs, 

 vary in size and proportions, and in their degree of union or 

 separation ; and if in one group of animals it was beneficial to 

 have the middle toe larger and longer, and in another set to 

 have the two middle toes of the same size, nothing can be 

 more certain than that these particular modifications would 

 be continuously preserved, and the very results we see ulti- 

 mately produced. 



The oft-repeated objections that the cause of variations is 

 unknown, that there must be something to determine variations 

 in the right direction ; that " natural selection includes no 

 actively progressive principle, but must wait for the develop- 

 ment of variation, and then, after securing the survival of the 

 best, wait again for the best to project its own variations for 

 selection," we have already sufficiently answered by showing 

 that variation — in abundant or typical species — is always 

 present in ample amount; that it exists in all parts and 

 organs ; that these vary, for the most part, independently, so 

 that any required combination of variations can be secured ; 

 and finally, that all variation is necessarily either in excess or 

 defect of the mean condition, and that, consequently, the right 

 or favourable variations are so frequently present that the 

 unerring power of natural selection never wants materials to 

 work upon. 



1 Origin of the Fittest, p. 374. 



