be pronounced to be strongly in favour of the view put forward by Brauer
(1869), and since supported by the great majority of naturalists who
have discussed the subject, that the caterpillar or the maggot is itself
a specialised product of the evolutionary process, adapted to its own
particular mode of larval life.

The explanation of insect transformation is, in brief, to be found in an
increasing amount of divergence between larva and imago. The most
profound metamorphosis is but a special type of growth, accompanied by
successive castings and renewings of the chitinous cuticle, which
envelopes all arthropods. In the simplest type of insect life-story,
there is no marked difference in form between the newly-hatched young
and the adult, and in such cases we find that the young insect lives in
the same way as the adult, has the same surroundings, eats the same
food. This is the rule (see Chapters II and III) with the Apterygota,
the Orthoptera, and most of the Hemiptera. In the last-named order,
however, we find in certain families marked divergence between larva and
imago, for example in the cicads, whose larvae live underground, while
in the coccids, whose males are highly specialised and females degraded,
there succeeds to the larva--very like the young stage in allied
families--a resting instar, which in the case of the male, suggests
comparison with the pupa of a moth or beetle.

Turning to the stone-flies, dragon-flies and may-flies, whose
life-stories have been sketched in Chapter IV, we find that the early
stages are passed in water, whence before the final moult, the insects
emerge to the upper air. Except for the possession of tufted gills,
adapting them to an aquatic life, the stone-fly nymphs differ but
slightly from the adults; the grubs of the dragon-flies and may-flies,
however, are markedly different from their parents. In connection with