Taking the facts as they now stand, it appears to me that the
order of the appearance of the sulci and gyri in the foetal human
brain is in perfect harmony with the general doctrine of
evolution, and with the view that man has been evolved from some
ape-like form; though there can be no doubt that form was, in
many respects, different from any member of the Primates now
living.

Von Baer taught us, half a century ago, that, in the course of
their development, allied animals put on at first, the characters
of the greater groups to which they belong, and, by degrees,
assume those which restrict them within the limits of their
family, genus, and species; and he proved, at the same time, that
no developmental stage of a higher animal is precisely similar to
the adult condition of any lower animal. It is quite correct to
say that a frog passes through the condition of a fish, inasmuch
as at one period of its life the tadpole has all the characters
of a fish, and if it went no further, would have to be grouped
among fishes. But it is equally true that a tadpole is very
different from any known fish.

In like manner, the brain of a human foetus, at the fifth month,
may correctly be said to be, not only the brain of an ape, but
that of an Arctopithecine or marmoset-like ape; for its
hemispheres, with their great posterior lobster, and with no
sulci but the sylvian and the calcarine, present the
characteristics found only in the group of the Arctopithecine
Primates. But it is equally true, as Gratiolet remarks, that, in
its widely open sylvian fissure, it differs from the brain of any