tinctive of sundry allied, though now extinct species, speaks
strongly in favour of evolution. For as it is of the essence of this
theory that new forms arise from older forms by way of _hereditary_
descent, we should antecedently expect, if the theory is true, that the
phases of development presented by the individual organism would follow,
in their main outlines, those phases of development through which their
long line of ancestors had passed. The only alternative view is that as
species of deer, for instance, were separately created, additional
prongs were successively added to their antlers; and yet that, in order
to be so added to successive species every individual deer belonging to
later species was required to repeat in his own lifetime the process of
successive additions which had previously taken place in a remote series
of extinct species. Now I do not deny that this view is a possible view;
but I do deny that it is a probable one. According to the evolutionary
interpretation of such facts, we can see a very good _reason_ why the
life-history of the individual is thus a condensed _resume_ of the
life-history of its ancestral species. But according to the opposite
view no reason can be assigned why such should be the case. In a
previous chapter--the chapter on Classification--we have seen that if
each species were created separately, no reason can be assigned why they
should all have been turned out upon structural patterns so strongly
suggestive of hereditary descent with gradual modifications, or slow
divergence--the result being group subordinated to group, with the most
generalized (or least developed) forms at the bottom, and the highest
products of organization at the top. And now we see--or shall
immediately see--that this consideration admits of being greatly
fortified by a study of the developmental history of every individual
organism. If it would be an unaccountable fact that every separately
created species should have been created with close structural
resemblances to a certain limited number of other species, less close
resemblances to certain further species, and so backwards; assuredly it
would be a still more unaccountable fact that every individual of every
species should exhibit in its own person a history of developmental
change, every term of which corresponds with the structural
peculiarities of its now extinct predecessors--and this in the exact
historical order of their succession in geo