668 The American Naturalist. [August, 
Conclusions.—The most impressive truth issuing from our 
review of recent researches in evolution and heredity is the 
uniformity of life-processes throughout the whole scale of life 
from the Infusoria to man. The most striking analogy is that 
seen in the laws of fertilization and conjugation, which are 
shown by Maupas’s researches to have been established sub- 
stantially in their present form at a very early period in the 
evolution of living organisms. Such uniformity furnishes a 
powerful argument for the advocates of the study of biology 
as an introduction to the applied science of medicine. Much 
that is now entirely omitted from medical education, because 
it is considered too remote, is in reality at the very roots of the 
science. To understand the disorders of life we should first 
thoroughly understand the essential phenomena of normal 
life. Of course we shall never see life as it really is, because 
there is always something beyond our highest magnifying 
powers; but we come nearest to this invisible form of energy 
when, with such investigators as Hertwig and Maupas, we 
strip the life-processes of all their accessories and view them 
in their simplest external form. 
The problems of evolution are found to be inseparably con- 
nected with those of heredity. No theory is at all adequate 
which does not explain both classes of facts, and we haveseen 
that the explanations offered by the two opposed schools— 
those who believe in the transmission of acquired characters 
and those who do not—are directly exclusive of each other. 
We should suspend judgment entirely rather than cease to 
gather from every quarter facts which bear upon the most 
important and central problem of the transmission of acquired 
characters. I have endeavored to point out the opportunities 
which medical practitioners enjoy of contributing evidence 
upon this mooted question. It must not be forgotten that 
while the inheritance of individual adaptation to environment 
is the simplest method of explaining race adaptation such as 
we observe in the evolution of man, we know absolutely 
nothing of how such inheritance can be effected through the 
germ-cells. We cannot at present construct even any form of 
working hypothesis for such a process. On the other hand, we 
