ia von Linden. In Eimer's
own laboratory the latter performed experiments on Papilionides, "which
prove in the most striking manner the recapitulation of the
family-history in the individual." "The fact that it is possible by
raising or lowering the temperature during the time of development to
breed butterflies, possessed of the characteristics of related
varieties and species living in southern and northern regions
respectively, characteristics not merely of color and design, but also
of structure, is complete irrefragable proof of my views."

Eimer therefore belongs to the class of naturalists, like Wigand,
Askenasy, Naegeli, and many others, who reject the purely mechanical
trend of Darwinism and recognize an "immanent principle of
development." He seeks the essential cause of evolution in the
constitution of the plasm of organisms. This very analogy between the
development of the family and that of the individual should, in fact,
convince any one of this. If Eimer chooses to refer the analogy to
"growth" and to designate the evolution of the whole animated kingdom
as also a process of growth, there is, strictly speaking, no room for
objection. However, there is here a danger, which he does not seem to
have guarded against. To designate the whole process as a growth, as
Eimer does, really explains nothing, but merely defines more clearly
the status of the problem. For, what do we know of the so-called
process of growth? In truth, nothing, so that very little is gained by
referring evolution to organic growth; the problem remains unsolved.

The most important and correct part of Eimer's conclusion seems to be
the establishment of definite lines of development. He has, in fact,
permanently disposed of the Darwinian assumption of universal chaos in
evolution, upon which good mother Nature could at will exercise her
choice. Fortuitously initiated development is a condition sine qua non
of Darwinism and Weismannism. For any one, who has studied the work of
Eimer and still adheres to this fundamental error of Darwinism, there
is no possible escape from the labyrinth into which he has allowed the
hand of Darwinism to lead him.

If, on the one hand, Eimer recognizes the immanent principles of
development, he, nevertheless, on the other hand, also accords due
consideration and ascribes great efficacy to external influences; in
fact, he represents them as perhaps the more essential factor. Climate,
nourishment, etc., affec