nimals, the phenomena of mimicry,
the protective arrangements of plants, the development of instinct in
animals, and the origin of flowers.

In reality Weismann only adduces _one_ strict proof, and even that is only
laying special stress on what is well known in comparative embryology;
namely, the possibility of "predicting" on the basis of the theory of
descent, as Leverrier "predicted" Neptune. For instance, in the lower
vertebrates from amphibians upwards there is an _os centrale_ in the
skeleton of wrist, but there is none in man. Now if man be descended from
lower vertebrates, and if the fundamental biogenetic law be true (that
every form of life recapitulates in its own development, especially in its
embryonic development, the evolution of its race, though with
abbreviations and condensations), it may be predicted that the _os
centrale_ is to be found in the early embryonic stages of man. And
Rosenberg found it. In the same way the "gill-clefts" of the fish-like
ancestors have long since been discovered in the embryo of the higher
vertebrates and of man. Weismann himself "predicted" that the markings of
the youngest stage of the caterpillars of the Sphingidae (hawk-moths) would
be found to be not oblique but longitudinal stripes, and ten years later a
fortunate observation verified the prediction. Because of the abundance of
evidential facts Weismann does not go into any detailed proof of
evolution. "One can hardly take up any work, large or small, on the finer
or more general structural relations, or on the development of any animal,
without finding in it proofs for the evolution theory."

But assured as the doctrine of descent appears,(12) and certain as it is
that it has not only maintained its hold since Darwin's day, but has
strengthened it and has gained adherents, this foundation of Darwinism is
nevertheless not the unanimous and inevitable conclusion of all scientific
men in the sense and to the extent that the utterances of Weismann and
others would lead us to suppose. Apart from all apologetic attempts either
in religious, ethical, or aesthetic interests, apart, too, from the
superior standpoint of the philosophers, who have not, so to speak, taken
the theory very seriously, but regard it as a provisional theory, as a
more or less necessary and useful method of grouping our ideas in regard
to the organic world, there are even among the biologists themselves some
who, indifferent towards religious or phil