t the inner structure, the plasm, transform it
and thus produce variation which is transmitted to the progeny. But,
however great may be the influence of environment, Eimer seems to
overestimate it. Indeed, the analogy of "growth" should have led Eimer
to a conception of the true relation between "internal" and "external"
causes. Warmth, air, light, moisture and nourishment, are undoubtedly
necessary factors in the process of growth, but they are only the
conditions which render it possible, and not the causes which produce
it. The latter are to be found in the individual organism itself. The
conditions may be ever so favorable and well-adapted for growth, still
the organism will not develop unless it bear within itself the power to
do so. On the other hand, although it is hampered and may become
abnormal, it will readily grow even in an unfavorable environment, as
long as it retains its inherent vital force. The same is very likely
true of the genealogical growth. Evolution took place in virtue of the
power inherent in the developing organisms. But only when the
environment was favorable and normal, did the evolution proceed
favorably and normally, that is, toward the perfection of the animate
kingdom.

It appears as if the internal principle of development were losing
influence and significance with Eimer; but the ulterior reason for this
is not far to seek. Whoever recognizes the validity of the internal
principle of development, eliminates chance, that stop-gap of
materialism, from evolution, and is lead at once to a supreme
Intelligence which directs evolution. As soon as it comes in sight,
however, certain persons take fright and turn aside or even turn back
in order to avoid it. This was the case with Eimer, although perhaps in
a lesser degree. This is sincerely to be deplored, since his theory
would have gained in depth if he had but done full justice to the
internal principle of development. For the same reason he seems to have
attacked Naegeli's principle of perfection, another fact which is very
much to be regretted. True, it is as anti-mechanical as it can be and
hence has gained but few adherents; but it is based on truth
nevertheless, and will some day prevail in the doctrine of Descent.

It is perfectly intelligible that the thought of "perfection" should
not have occurred to Eimer or should have slipped his memory during
his observations on butterflies. The fact however, reveals a
one-sidedness which h