adjusted
to its surroundings, but it further suggests that the animal by
gradual process has become thus adjusted. The word adaptation applies
not simply to the result, but also to the process. The scientist does
not consider the animal a final and complete result. He thinks it
still in a state of flux, and so long as its line lasts it will be in
a state of flux. Change is about it on every side, and it must adapt
itself to this change or it will pass away. It may adjust itself, as
has been previously stated, by moving to another environment in which
it feels more at home, but unless it does this, if there come much
change in its present surroundings, it must either meet the
difficulty by altering itself, or it must give up the struggle. The
alteration is unconscious so far as the animal is concerned. It is
seriously to be doubted whether there is any recognition of the
process on the part of any animal excepting man. But though the
process be unconscious, it is none the less there. Slowly and
gradually the animal and the environment are becoming adjusted to each
other.

While it is exceedingly difficult to lay our hands on any animal which
is at present visibly changing its structure, it is not hard to find
closely related animals. These are nearly alike in structure in most
respects. In a few points, however, they may differ materially, and
these points are often directly concerned with different habits of
life. Considered in this aspect, these adaptations of a single organ
separately examined form an excellent argument in favor of that
gradual alteration of the entire organism which evolution suggests.

The most primitive struggle in which an animal can possibly engage is
the effort to maintain its own life and vigor. This struggle will
result in certain adaptations for the individual, adjustments which
make for the safety of the animal himself. These form the subject
matter of the present chapter.

The farther up the animal kingdom we pass in the study of adaptation,
the more likely we are to find changes which have but little bearing
on the safety of the individual. They work for the good of the entire
species, sometimes to the distinct disadvantage of the individual. The
King Salmon may make its long run to the headwaters of our western
rivers, deposit its eggs, have them fertilized, and then float down to
death. But it does not die before abundant preparation has been made
for the continuance of the race. Su