560
Mr. Spencer says that the introduction of new organs
could not be explained by the principle of the inherited
effects of use and disuse, and he therefore infers that this
phenomenon must have been brought about by Natural
Selection. But, as we have already shown, the evolution
of the electric organ in certain fishes cannot be explained
on the principles of Natural Selection. On the contrary,
it is readily admitted that it offers the greatest difficulty to
the acceptance of the theory.
Mr. Spencer argues that:—
“ the relations of tendons to bones and to one another, are not always
the same. Variations in their modes of connection may occasionally
prove advantageous, and may thus become established. Here again,
then, we have a class of structural changes to which Mr. Darwin’s
hypothesis gives us the key, and to which there is no other key.”—
(p. 8.)
I am in ignorance of the precise nature of the facts
from which Mr. Spencer draws this very important in
ference. But we may remark that the case, as put by
Mr. Spencer, is altogether hypothetical. He does not
prove that some of these variations must be useful ; he
simply asserts that they may be useful. But they must be
useful—they must secure the survival of those who possess
these modifications, while the others, not so modified, are
destroyed—if they are to be referred to a class of structural
changes to which Mr. Darwin’s hypothesis gives us the
key.
And then, what are we to say as to the assertion that
there is no other key than that of Natural Selection to
explain this phenomenon. What is the phenomenon ?
“ The relations of bones to tendons are not always the
same.” That, I suppose, means that the tendons are not
always attached to exactly the same point. But the fact
that such variations are to be found, seems to indicate that