ific members of the human family, it would be a mistake to
suppose that it is this class of facts that the worker is particularly
seeking. The truth is that, as a rule, the pure biologist is engaged in
work for the love of it, and nothing is further from his thoughts than
the "practical" bearings or remote implications of what he may discover.
Indeed, many of his most hotly pursued problems seem utterly divorced
from what an outsider would call practical bearings, though, to be
sure, one can never tell just what any new path may lead to. Such, for
example, is the problem which, next to questions of cell activities,
comes in for perhaps as large a share of attention nowadays as any other
one biological topic;--namely, the question as to just which of
the various orders of invertebrate creatures is the type from which
vertebrates were evolved in the past ages--in other words, what
invertebrate creature was the direct ancestor of the vertebrates,
including man. Clearly it can be of very little practical importance to
man of to-day as to just who was his ancestor of several million years
ago. But just as clearly the question has interest, and even the layman
can understand something of the enthusiasm with which the specialist
attacks it.

As yet, it must be admitted, the question is not decisively answered,
several rival theories contending for supremacy in the case. One of
the most important of these theories had its origin at the Naples
laboratory; indeed, Dr. Dohrn himself is its author. This is the view
that the type of the invertebrate ancestor is the annelid--a form whose
most familiar representative is the earth-worm. The many arguments for
and against accepting the credentials of this unaristocratic ancestor
cannot be dwelt upon here. But it may be consolatory, in view of the
very plebeian character of the earth-worm, to know that various of the
annelids of the sea have a much more aristocratic bearing. Thus the
filmy and delicately beautiful structures that decorate the pleasant
home of the quaint little seahorse in the aquarium--structures having
more the appearance of miniature palm-trees than of animals--are really
annelids. One can view Dr. Dohrn's theory with a certain added measure
of equanimity after he learns this, for the marine annelids are seen,
some of them, to be very beautiful creatures, quite fitted to grace
their distinguished offspring should they make good their ancestral
claims.

These glimpses