Studies in the Theory of Descent, Volume I

by August Weismann

I.

The Origin and Significance of Seasonal Dimorphism, p. [1].

Historical preliminaries, [1]. Does not occur in other orders of insects, [4]. Beginning of experimental investigation, [5]. Lepidopterous foes, [7]. First experiments with Araschnia Levana, [10]. Experiments with Pieris Napi, [13]. Discussion of results, [17]. Origination of Prorsa from Levana, [19]. Theoretical considerations, [23]. The case of Papilio Ajax, [30]. Experiments with Pieris Napi var. Bryoniæ, [39]. The summer generations of seasonally dimorphic butterflies the more variable, [42].

II.

Seasonal Dimorphism and Climatic Variation, p. [45].

Distinction between climatic and local varieties, [45]. The case of Euchloe Belia and its varieties, [47]. The case of Polyommatus Phlæas, [49]. The case of Plebeius Agestis, [50].

III.

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].