Studies in the Theory of Descent (Volumes 1 and 2)

A series of detailed empirical studies of insects combines observation and experiment to explain protective coloration, seasonal dimorphism, and other recurring morphological patterns. The work uses developmental and comparative evidence to explore heredity, arguing for a germ-plasm view that limits inheritance of acquired traits, and discusses the role of natural selection, embryological stages, and age-dependent characters in classification, offering theoretical reflections on the sources and transmission of variation.