reader will have realised by this time--and many of the positions
confidently adopted in the earlier constructive stage are challenged.
This applies to the protective colours, warning colours, mimicry, etc.,
of insects. Probably some of the affirmations of the older generation of
evolutionists were too rigid and extensive; and probably the denials of
the new generation are equally exaggerated. When all sound criticism has
been met, there remains a vast amount of protective colouring, shaping,
and marking in the insect world of which natural selection gives us the
one plausible explanation. But the doctrine of natural selection does
not mean that every feature of an animal shall have a certain utility.
It will destroy animals with injurious variations and favour animals
with useful variations; but there may be a large amount of variation,
especially in colour, to which it is quite indifferent. In this way much
colour-marking may develop, either from ordinary embryonic variations
or (as experiment on butterflies shows) from the direct influence of
surroundings which has no vital significance. In this way, too, small
variations of no selective value may gradually increase until they
chance to have a value to the animal. [*]

* For a strong statement of the new critical position see
Dewar and Finn's "Making of Species," 1909, ch. vi.

The origin of the metamorphosis, or pupa-stage, of the higher
insects, with all its wonderful protective devices, is so obscure and
controverted that we must pass over it. Some authorities think that
the sleep-stage has been evolved for the protection of the helpless
transforming insect; some believe that it occurs because movement would
be injurious to the insect in that stage; some say that the muscular
system is actually dissolved in its connections; and some recent experts
suggest that it is a reminiscence of the fact that the ancestors of the
metamorphosing insects were addicted to internal parasitism in their
youth. It is one of the problems of the future. At present we have no
fossil pupa-remains (though we have one caterpillar) to guide us. We
must leave these fascinating but difficult problems of insect life, and
glance at the evolution of the birds.

To the student of nature whose interest is confined to one branch
of science the record of life is a mysterious Succession of waves. A
comprehensive view of nature, living and non-living, past and present,
discovers scores