There is, however, no clear evidence that one of these
constantly appears before the other; and it is remarkable that,
in the brain at the period described and figured by Ecker (loc.
cit. pp. 212-213, Taf. II, figs. 1, 2, 3, 4), the antero-temporal
sulcus (scissure parallele) so characteristic of the ape's brain,
is as well, if not better developed than the fissure of Rolando,
and is much more marked than the proper frontal sulci.
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.
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