examination of the structure of this surface that we reconstruct in
imagination the whole system of branches, and know that certain twigs,
from their likeness, meet each other a little way down; that others
are connected only very deep down, and that others, again, spring
free almost from the beginning. The fossils of beds of rock of
different geological ages give us incomplete views of the surface of
the thicket of life, as it was in earlier times. These views we have
of the past aspects of the animal kingdom are always much more
incomplete than our knowledge of the existing aspect; partly because
many animals, from the softness of their bodies, have left either no
fossil remains at all, or only very imperfect casts of the external
surfaces of their bodies; and partly because the turning of any animal
into a fossil, and its subsequent discovery by a geologist, are
occasional accidents; but, although the evidence is much less perfect
than we could wish, there is enough of it to convince anatomists that
existing animals are all in definite blood-relationship to each other,
and to make them, in the investigation of any new animal, study its
anatomy with the definite view of finding out its place in the family
tree of the living world.

When Huxley made his first discoveries, entirely different ideas
prevailed. The animal kingdom was supposed to offer a series of types,
of moulds, into which the Creator at the beginning of the world had
cast the substance of life. These types were independent of each
other, and had been so since the beginning of things. Anatomists were
concerned chiefly with systematic work, with detecting and recording
the slight differences that existed among the numbers of animals
grouped around each type. No attempt was made to see connection
between type and type, for where these had been separately created
there was nothing to connect them except possibly some idea in the
mind of the Creator. This apparently barren attitude to nature was
stronger in men's minds because it had inspired the colossal
achievements of Cuvier, a genius who, under whatever misconceptions he
had worked, would have added greatly to knowledge. As we have seen in
the first chapter, Huxley, through Wharton Jones, and through his own
reading, had been brought under the more modern German thought of
Johannes Mueller and Von Baer. He had learned to study the problems of
living nature in the spirit of a physicist making investigati