climatic environment of the pupa. The experiments of Weismann just
sketched in outline show at least that the same principle holds for our
northern butterflies.

We are thus led to see from the life-story of such insects, that the
course of the story is not rigidly fixed; the creature in its various
stages is plastic, open to influence from its surroundings, capable of
marked change in the course of generations. And so the seasonal changes
in the history of the individual from egg to imago point us to changes
in the age-long history of the race.




CHAPTER IX

PAST AND PRESENT; THE MEANING OF THE STORY


In the previous chapter we recognised how the seasonal changes in
various species of butterflies as observable in two or three
generations, indicate changes in the history of the race as it might be
traced through innumerable generations. The endless variety in the form
and habits of insect-larvae and their adaptations to various modes of
life, which have been briefly sketched in this little book, suggest
vaster changes in the class of insects, as a whole, through the long
periods of geological time. Every student of life, influenced by the
teaching of Charles Darwin (1859) and his successors, now regards all
groups of animals from the evolutionary standpoint, and believes that
comparisons of facts of structure and life-history of orders and classes