SOME BIOLOGICAL PROBLEMS.
15
proofs of the inheritance of acquired characters, but are more
probably examples of what is termed "parallel induction."
By this term is understood the action of the environment upon
"both the body cells and the germ cells in the same way, simul-
taneously but independently, without modification of the
fundamental constitution of the germ plasm.
Coming to what may be called the evolutionary problems
there are two which may claim our attention for a few minutes.
The first of these is the extremely important one whether the
characters which we use in the separation of allied species have
any survival value for the animals. From the point of view
of evolution by natural selection pure and simple all characters
should be now, or must have been in the past, of some use to
their possessors. But when one comes to examine groups of
closely allied species it is very often exceedingly difficult to
imagine what benefit the animals (and plants) can possibly
derive from the different little variations of this and that
detail. This difficulty is well known to all specialists and has
been so much taken to heart by some naturalists that the
conception of natural selection as a factor of any significance
in evolution has been doubted. This, I believe, to be an un-
reasonable attitude in view of the evidence on every side of
selection taking place in nature, but it is as well that the
apparent non-survival value of many specific characters should
be kept in mind. The discovery of the real significance of such
characters will undoubtedly mark an important step forward
in biological science. As a possible illustration of these specific
characters which defy all attempts to ascribe to them any useful
function, we may take the fifth feet of species of the genus
Cyclops. These organs it is true are much reduced as compared
with the four preceding pairs of feet, and as compared with
their homologues in some other genera of Copepods. But they
have very definite shapes and armature in the different species,
and are scarcely at all variable, thus giving one the impression
that they should be of importance. They are much too small,
however, to be of any use in swimming, and as they are the
same in both sexes they cannot function in connection with
reproduction as is the case with the corresponding feet in many
other Copepods. On the whole it looks as if the most we can
postulate about them as regards any possible usefulness is that