that we can grasp how these highest and most striking faculties of the
animal organism have been historically evolved. In other words, a
knowledge of the evolution of the spinal cord and brain in the human
embryo leads us directly to a comprehension of the historic
development (or phylogeny) of the human mind, that highest of all
faculties, which we regard as something so marvellous and supernatural
in the adult man. This is certainly one of the greatest and most
pregnant results of evolutionary science. Happily our embryological
knowledge of man's central nervous system is now so adequate, and
agrees so thoroughly with the complementary results of comparative
anatomy and physiology, that we are thus enabled to obtain a clear
insight into one of the highest problems of philosophy, the phylogeny
of the soul, or the ancestral history of the mind of man. Our chief
support in this comes from the embryological study of it, or the
ontogeny of the soul. This important section of psychology owes its
origin especially to W. Preyer, in his interesting works, such as The
Mind of the Child. The Biography of a Baby (1900), of Milicent
Washburn Shinn, also deserves mention. [See also Preyer's Mental
Development in the Child (translation), and Sully's Studies of
Childhood and Children's Ways.]

In this way we follow the only path along which we may hope to reach
the solution of this difficult problem.

Thirty-six years have now elapsed since, in my General Morphology, I
established phylogeny as an independent science and showed its
intimate causal connection with ontogeny; thirty years have passed
since I gave in my gastraea-theory the proof of the justice of this,
and completed it with the theory of germinal layers. When we look back
on this period we may ask, What has been accomplished during it by the