sture in the air, and
all other conditions of existence, influence the living organism. And they
do so not indirectly, as is implied in the process of selection, simply
playing the part of a sieve, and not themselves moulding and transforming,
but _directly_ by necessitating the production of new developments in the
living substance, new chemical and physiological activities, new groupings
and changes of form, and new organs.

Darwin himself did not regard these two theories as opposed to the theory
of selection, but utilised them as subsidiary interpretations. It is
obvious, however, that at bottom they conceal an essentially different
fundamental idea, which, if followed out to its logical consequences,
reduces the "struggle for existence" to at most a wholly indifferent
accessory circumstance. Weismann felt this, and hence his entirely
consistent endeavours to show by great examples, such as the origin of
flowers, the mutual adaptations of flowers and insects, the phenomena of
mimicry, and many other cases, that neither the Lamarckian nor any other
factor in evolution, except only natural, passive selection, suffices as
an interpretation. From the Darwinian standpoint he is absolutely right,
and must needs speak of the "omnipotence of natural selection," for it
must either be omnipotent, or it must give place to the other two factors,
and retain only the significance we attributed to it in another connection
(p. 157), which amounts to saying none at all. It is obvious enough why
the discussion as to these factors should centre round the question of the
"inheritance of acquired characters," "acquired" either through the use or
disuse of organs, the exercise or non-exercise of functions, or through
the stimuli of the external world.

The neo-Lamarckian conflict with Darwinism has become more and more acute
in recent times, and the neo-Lamarckians have sometimes passed from
contrasting rival interpretations to excluding the Darwinian factor
altogether. As the particular champion of the neo-Lamarckian view, we must
name Th. Eimer, the recently deceased Tuebingen zoologist. His chief work
is in three volumes, entitled "Die Entstehung der Arten auf Grund von
Vererbung erworbener Eigenschaften, nach Gesetzen organischen
Wachsens."(43) It is a polemic against Weismannism in all details, even to
the theory of "germinal selection." Eimer follows in the footsteps of St.
Hilaire, and shows what a relatively plastic and sensitive