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. 
