d in the right cavity.
"Poor little beggar," said Huxley; "I never could get them myself
until I reflected that a bishop could never be in the right." This
insistence on the uselessness of formal knowledge applied only to
those who were being taught or who were learning from books or
lectures. Of the value and discipline of knowledge of facts gained at
first hand from objects themselves either in original investigation or
with the aid of books, Huxley had the highest possible opinion. By
such a method of work alone he believed it possible to distinguish
what we believe on authority from what we have convinced ourselves to
be true, and, as we shall see later, he regarded it as the most
important duty of a man to have acquired the habit of classifying the
mass of ideas in his brain into those which he knew and those which he
thought to be true from having read or heard or imagined them.

The two other of the three great treatises for anatomical students are
the _Manual of the Anatomy of Vertebrated Animals_, published in 1871,
and the _Manual of the Anatomy of Invertebrated Animals_, published in
1877. Of these two volumes it is sufficient to say that they formed
the chief introduction to the study of animal zooelogy for many years,
and that a large number of the best-known zooelogists of the end of
this century received from them their first instruction in the
science. As text-books they have been superseded lately by larger
volumes in which there is found more space for some of the recent
advances in knowledge, especially comparative embryology, and the more
intricate knowledge of the structure of the soft parts of marine
invertebrates made possible by the newer and more successful methods
of preserving delicate tissues. Just before Huxley ceased his regular
work as a teacher at the Royal College of Science, there arrived a
series of marine embryos, beautifully preserved and prepared for
microscopic work by the zooelogists at the International Zooelogical
Station at Naples. Huxley is reported to have exclaimed at their
beauty, and to have said: "You young men cannot realise your
advantages; you have brought to you for study at your leisure in
London, creatures that I had to lash my microscope to the mast to get
a glimpse of." Huxley's books were written for students with fewer
advantages, and, naturally, laid more stress on the harder skeletal
parts and such structures as could be more easily preserved; but with
this i