ions of the skull and of the backbone were laid
down in a fashion quite different, and that it was impossible to
regard both skull and backbone as modifications of a common type
laid down right along the axis of the body. The spinal column and
the skull start from the same primitive condition, whence they
immediately begin to diverge. It may be true to say that there is
a primitive identity of structure between the spinal or vertebral
column and the skull; but it is no more true that the adult skull
is a modified vertebral column than it would be to affirm that
the vertebral column is a modified skull."

Since this famous lecture, a number of distinguished anatomists have
studied the development of the skull more fully; but they have not
departed from the methods of investigation laid down by Huxley, and
their conclusions have differed only in greater elaboration of detail
from the broad lines laid down by him. Apart from its direct
scientific value, this lecture was of importance as marking the place
to which Huxley had attained in the scientific world. Two years later,
it is true, the London _Times_, referring to a famous debate at a
meeting of the British Association at Oxford, spoke of him as "a Mr.
Huxley"; but in the scientific world he was accepted as the leader of
the younger anatomists, and as one at least capable of rivalling Owen,
who was then at the height of his fame. The Croonian Lecture was in a
sense a deliberate challenge to Owen, and in these days before Darwin,
to challenge Owen was to claim equality with the greatest name in
anatomical science.

CHAPTER V

CREATURES OF THE PAST

Beginning Palaeontological Work--Fossil Amphibia and
Reptilia--Ancestry of Birds--Ancestry of the Horse--Imperfect
European Series Completed by Marsh's American Fossils--Meaning of
Geological Contemporaneity--Uniformitarianism and Catastrophism
Compared with Evolution in Geology--Age of the
Earth--Intermediate and Linear Types.

Although Huxley took a post connected with Geology only because it was
the most convenient opening for him, it was not long before he became
deeply interested not only in the fossils, which at first he despised,
but in the general problems of geology. He began by co-operation with
Mr. Salter in the determination of fossils for the Geological Survey.
The mere work of defining genera and species and naming and descr