duty lies my excuse for the publication of these essays. For it
will be admitted that some knowledge of man's position in the animate
world is an indispensable preliminary to the proper understanding of his
relations to the universe--and this again resolves itself, in the long
run, into an inquiry into the nature and the closeness of the ties which
connect him with those singular creatures whose history [1] has been
sketched in the preceding pages.

The importance of such an inquiry is indeed intuitively manifest Brought
face to face with these blurred copies of himself, the least thoughtful
of men is conscious of a certain shock, due perhaps, not so much to
disgust at the aspect of what looks like an insulting caricature, as
to the awakening of a sudden and profound mistrust of time-honoured
theories and strongly-rooted prejudices regarding his own position in
nature, and his relations to the under-world of life; while that which
remains a dim suspicion for the unthinking, becomes a vast argument,
fraught with the deepest consequences, for all who are acquainted with
the recent progress of the anatomical and physiological sciences.

I now propose briefly to unfold that argument, and to set forth, in
a form intelligible to those who possess no special acquaintance
with anatomical science, the chief facts upon which all conclusions
respecting the nature and the extent of the bonds which connect man with
the brute world must be based: I shall then indicate the one immediate
conclusion which, in my judgment, is justified by those facts, and I
shall finally discuss the bearing of that conclusion upon the hypotheses
which have been entertained respecting the Origin of Man.

The facts to which I would first direct the reader's attention, though
ignored by many of the professed instructors of the public mind, are
easy of demonstration and are universally agreed to by men of science;
while their significance is so great, that whoso has duly pondered over
them will, I think, find little to startle him in the other revelations
of Biology. I refer to those facts which have been made known by the
study of Development.

It is a truth of very wide, if not of universal, application, that every
living creature commences its existence under a form different from, and
simpler than, that which it eventually attains.

[Illustration: FIG. 12.--A. Egg of the Dog, with the vitelline membrane
burst, so as to give exit to the yelk, the ger