75] were the first to investigate the subject systematically,
choosing for their work the egg of the frog.[476] Roux continued for many
years to follow up this line of work.[477]

In 1890 he drew up a programme and manifesto[478] of
_Entwicklungsmechanik_ as "an anatomical science of the future," and in
1895 he founded the famous _Archiv fuer Entwicklungsmechanik_,[479]
publishing in the same year the two large volumes of his collected
papers,[480] of which the first volume dealt with functional adaptation,
the second with experimental embryology.

His subsequent work includes several important general papers;[481]
besides a number of special memoirs dealing with the factors of
development, and with his original subject, functional adaptation.[482]

In our sketch of his views we shall have occasion to refer particularly
to his publications of 1881, 1895 (the _Einleitung_), 1902, 1905, and
1910.

Although Roux's biological philosophy is out-and-out mechanistic, he yet
recognises the difficulty, even the impossibility, of straightway
reducing development to the physico-chemical level. He tries to steer a
course midway between the simplicist conceptions of the materialists and
the "metaphysics" of the neo-vitalist school, which the experimental
study of development and regeneration soon brought into being. In 1895
he writes:--"The too simple mechanistic conception on the one hand, and
the metaphysical conception on the other represent the Scylla and
Charybdis, between which to sail is indeed difficult, and so far by few
satisfactorily accomplished; it cannot be denied that with the increase
of knowledge the seduction of the second has lately notably increased"
(p. 23).

The _via media_ adopted by Roux is the analysis of development, not
directly into simple physico-chemical processes, but into more complex
organic processes dependent upon the fundamental properties of living
matter. The aim of _Entwicklungsmechanik_ is defined by Roux to be the
reduction of developmental events to the fewest and simplest
_Wirkungsweisen_, or causal processes.[483] Two classes of causal
processes may be distinguished, as "complex components" and "simple
components" of development. The latter are directly explicable by the
laws of physics and chemistry; the former, while in essence
physico-chemical, are yet so very complicated that they cannot at
present be reduced to physico-chemical terms. The ultimate aim of
_Entwicklungsmechanik_ i