_Nature of the Causes producing Climatic Varieties_, p. 52.
Seasonal dimorphism of the same nature as climatic variation, 52.
How does climatic change influence the markings of a butterfly? 52.
The cause of this to be found in temperature, 54. Part played by the
organism itself, 58. Analogous seasonal dimorphism in _Pierinæ_, 60.
The part played by sexual selection, 62.