ification must be more or less arbitrary,
and in a sense false; that it is at best only a verbal convenience, not
the embodiment of a final ideal. If, for example, we consider the very
"natural" group of birds commonly called hawks, we are quite justified
in dividing this group into several genera or minor groups, each
composed of several species more like one another than like the members
of other groups of species--that is, of other genera. But in so doing we
must remember that if we could trace the ancestry of our various species
of hawks we should find that in the remote past the differences that now
separate the groups had been less and less marked, and originally
quite non-existent, all the various species having sprung from a common
ancestor. The genera of to-day are cousin-groups, let us say; but the
parents of the existing species were of one brood, brothers and sisters.
And what applies to the minor groups called genera applies also, going
farther into the past, to all larger groups as well, so that in the last
analysis, all existing creatures being really the evolved and modified
descendants of one primordial type, it may be said that all animate
creation is but a single kind. In this broadened view the details of
classification ceased to have the importance once ascribed to them, and
the quibblings of the classifiers seem amusing rather than serious.
Yet the changed point of view left the subject by no means barren of
interest. For if the multitudinous creatures of the living world are
but diversified twig-lets of a great tree of ascent, spread by branching
from a common root, at least it is worth knowing what larger branches
each group of twiglets--representing a genus, let us say--has sprung
from. In particular, since the topmost twig of the tree is represented
by man himself and his nearest relatives, is it of human interest to
inquire just what branches and main stems will be come upon in tracing
back the lineage of this particular offshoot. This attempt had, perhaps,
no vast, vital importance in the utilitarian sense in which these terms
are oftenest used, but at least it had human interest. Important or
otherwise, it was the task that lay open to zoology, and apparently its
only task, so soon as the Darwinian hypothesis had made good its status.
The man who first took this task in hand, and who has most persistently
and wisely followed it, and hence the man who became the recognized
leader in the field o