symmetrical divided hoofs of our deer and cattle. The fact 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."[205]

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 ultimately 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 development 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.

_Supposed Action of Animal Intelligence._

The following passage briefly summarises Mr. Cope's position:
"Intelligence is a conservative principle,