1, 1906, b).

The concept of homology has thus a value quite independent of any
evolutionary interpretation which may be superadded to it. "Homology is
a mental concept obtained by comparison, which under all circumstances
retains its validity, whether the homology finds its explanation in
common descent or in the common laws that rule organic development" (p.
151, 1906, b). As A. Braun long ago pointed out, "It is not descent
which decides in matters of morphology, but, on the contrary, morphology
which has to decide as to the possibility of descent."[541]

Hertwig, in a word, reverts to the pre-evolutionary conception of
homology. "We see in homology," he writes, "only the expression of
regularities (_Gesetzmaessigkeiten_) in the organisation of the animals
showing it, and we regard the question, how far this homology can be
explained by common descent and how far by other principles, as for the
present an open one, requiring for its solution investigations specially
directed towards its elucidation" (p. 179, 1906, b).

Holding, as he does, that no definite conclusions can be drawn from the
facts of comparative anatomy and embryology as to the probable lines of
descent of the animal kingdom, Hertwig accords very little value to
phylogenetic speculation. It is, he admits, quite probable that the
archetype of a class represents in a general sort of way the ancestral
form, but this does not, in his opinion, justify us in assuming that
such generalised types ever existed and gave origin to the present-day
forms. "It is not legitimate to picture to ourselves the ancestral forms
of the more highly organised animals in the guise of the lower animals
of the present day--and that is just what we do when we speak of
Proselachia, Proamphibia and Proreptilia" (p. 155, 1906, b).

He rejects on the same general grounds the evolutionary dogma of
monophyletic or almost monophyletic descent, and admits with Koelliker,
von Baer, Wigand, Naegeli and others that evolution may quite well have
started many times and from many different primordial cells.

There is indeed a great similarity between the views developed by O.
Hertwig and those held by the older critics of Darwinism--von Baer,
Koelliker, Wigand, E. von Hartmann and others. It is true the
philosophical standpoint is on the whole different, for while many of
that older generation were vitalists Hertwig belongs to the mechanistic
school.

But both Hertwig and the older schoo