The law of wave-like
development (during the course of the formation of the individual
organism a series of changes proceed in a definite direction over the
body of the animals). (6). The law of independent uniformity of
development (the same course of development is pursued in non-related
forms and results in similar forms). (7). The law of development
through different stages (different characteristics of the same being
may develop to a different degree and in different directions). (8).
The law of unilateral development (the progeny does not present a
complete combination of the characters of the parents but manifests a
preponderance of the characteristics of either parent). (9). The law of
the reversal of development (the direction of development may reverse
and tend towards the starting point). (10). The law of the cessation of
development (a protracted cessation of development frequently ensues in
one or the other stage).

The origin (perhaps rather the distinction) of species is accounted for
principally by the last named law, by means of which Eimer also
explains the so-called atavism or reversion. To this law are joined
other factors, e.g., development proceeding in leaps, as demonstrated
by Koelliker and Heer; local separation (through migration; prevention
of fertilization, e.g., the impossibility of cross-fertilization
between certain individual organisms) which Romanes had already opposed
to natural selection, and crossing.

The second main division of the book is taken up with a very searching
and detailed criticism of Weismann. This criticism seems to me entirely
warranted; because not only the latter's unintelligible position with
regard to natural selection (the repudiation of which he seems to
regard as synonymous "with cessation of all investigation into the
causal nexus of phenomena in the domain of life") but likewise his
fanciful theory of heredity, utterly devoid as it is of any support
from actual observation, bespeak an utter lack of qualities essential
to a naturalist; and the manner in which he ignores his former pupil
and his labors, because they proved embarrassing to him, is entirely
unworthy of a man of science.

Eimer devotes special attention to "mimicry"; and indeed he was forced
to be very solicitous to dispel this fanciful conception of Darwinism
which radically contradicted his own views. Moreover, the untenableness
of the mimicry hypothesis must have revealed itself very clearly