have seemed a remoter or more unlikely comparison
than one instituted between Medusae and the embryonic stages of
back-boned animals. But Huxley made it, not allowing the evidence
brought before his reason to be swamped by preconceived ideas. At the
time he did no more than to make the comparison. It was much later
that the full importance of it became known, when more extended work
on the embryology of vertebrates and of the different groups of the
invertebrates had made it plain that the two foundation-membranes of
Huxley occur in all animals from the Medusae up to man. In the group of
Coelenterata the organisation remains throughout life as nothing
more than a folding in and folding out of these membranes. The early
stages of all the higher animals similarly consist of complications of
the two membranes; but later on there is added to them a third
membrane. Thus the group that Huxley gathered together comprises those
animals that as adults remain in a condition of development which is
passed through in the embryonic life of all higher animals. The
immense importance of this conclusion becomes plain, and the
conclusion itself seems obvious, when seen in the light of the
doctrine of descent. The group of Coelenterata represents a
surviving, older condition in the evolution of animals. Huxley
himself, when on the _Rattlesnake_, regarded evolution only as a vague
metaphysical dream, and he made the comparison which has been
described without any afterthought of what it implied. In this we have
the earliest authentic instance of the peculiar integrity of mind
which was so characteristic of him in his dealings with philosophy and
tradition. He never allowed any weight of authority or any apparent
disturbance of existing ideas to alter the conclusions to which his
reason led him. This intellectual courage made him fitted to be the
leader in the battle for evolution and against traditional thought,
and we shall find again and again in consideration of his work that it
was the keynote of his life.

CHAPTER IV

EARLY DAYS IN LONDON

Scientific Work as Unattached Ship-Surgeon--Introduction to
London Scientific Society--Translating, Reviewing, and
Lecturing--Ascidians--Molluscs and the Archetype--Criticism of
Pre-Darwinian Evolution--Appointment to Geological Survey.

The _Rattlesnake_ was paid off at Chatham on November 9, 1850. In the
natural course of events Huxley would have been appointed b