172 HERBERT SPENCER

elusion that bodily modifications due to use or disuse
or environmental influence can be as such or in any
representative degree transmitted, is very weak. The
so-called evidences are often anecdotal and vague,
often irrelevant and fallacious, and those Spencer
adduced are by no means convincing. Let us con-
sider the question briefly from the a priori side.

The general argument against the hypothesis rests
on a realisation of the continuity of the germ-plasm.
For if the germ-plasm, or the material basis of in-
heritance within the germ-cells, be somewhat apart
from the general life of the body, often segregated at
an early stage, and in any case not directly sharing in
the every day metabolism, then there is a presumption
against the likelihood of its being readily affected in a
specific manner by changes in the nature of the body-
cells. The germ-cell is in a sense so apart that it is
difficult to conceive of the mechanism by which it
might be influenced in a specific or representative
manner by changes in the cells of the body.

On the other hand, in many plants and lower
animals, the distinction between body-cells and germ-
cells is far from being demonstrably marked, and
even in higher animals we cannot think of the germ-
ceils as if they led a charmed life uninfluenced by any
of the accidents and incidents in the daily life of the
body which is their nurse, though not exactly their
parent. No one believes this, Weismann least of all,
for he finds one of the chief sources of germinal
variation in the nutritive stimuli exerted on the germ-
plasm by the varying state of the body. The
organism is a unity; the blood and lymph and other
body-fluids form a common internal medium \ varioust, in the individual life, what the evidence shows