this from the fact that the organ of reproduction stands in closer
and more important relation to the remaining parts, and especially to
the nervous system, than do the other organs; and, inversely, that
both the perceived and unperceived events affecting the whole
organism find a more marked response in the reproductive system than
elsewhere.

We can now see with sufficient plainness in what the material
connection is established between the acquired peculiarities of an
organism, and the proclivity on the part of the germ in virtue of
which it develops the special characteristics of its parent.

The microscope teaches us that no difference can be perceived between
one germ and another; it cannot, however, be objected on this account
that the determining cause of its ulterior development must be
something immaterial, rather than the specific kind of its material
constitution.

The curves and surfaces which the mathematician conceives, or finds
conceivable, are more varied and infinite than the forms of animal
life. Let us suppose an infinitely small segment to be taken from
every possible curve; each one of these will appear as like every
other as one germ is to another, yet the whole of every curve lies
dormant, as it were, in each of them, and if the mathematician
chooses to develop it, it will take the path indicated by the
elements of each segment.

It is an error, therefore, to suppose that such fine distinctions as
physiology must assume lie beyond the limits of what is conceivable
by the human mind. An infinitely small change of position on the