SEASONAL DIMORPHISM OF LEPIDOPTERA. 29 



capsidae, but nevertheless alarming : let us hope it is not going 

 to be as serious a pest to the walnut as it is to the apple, and 

 sometimes pear. 



Wye Court, near Ashford, Jan. 3rd, 1896. 



NEW EXPEEIMENTS ON THE SEASONAL DIMOEPHISM 

 OF LEPIDOPTERA. 



By Dr. August Weismann. 



(Translated from the German by W. E. Nicholson, F.E.S.) 



The following treatise contains an exhaustive account of a 

 series of experiments, which I have made with various butterflies 

 during the last decade, in order to obtain an assured answer to 

 the question, which was suggested rather than solved in my first 

 pamphlet, ' Ueber den Saison-Dimorphismus der Schmetterlinge.' 

 I was able then (1875) to prove, what Dorfmeister had already, 

 indeed, shown was probable for Vanessa levana, that with various 

 seasonally-dimorphic species the forms, which alternate under 

 the influence of warmth or cold, can to some extent be even con- 

 verted one into the other. I had also sought to form some 

 conception of how the phyletic origin of such dimorphism in a 

 species could be considered as the effect of alternating climatic 

 influences, but this was only an experiment, which I was far 

 from considering as the final settlement of the whole question. I 

 therefore made use of time and opportunity, when available, in 

 order to obtain, by new experiments, more precise answers to the 

 questions, how far the phenomenon of seasonal dimorphism in 

 general might be produced by the direct effect of temperature, 

 and how far changes of climate might produce permanent, i. e. 

 hereditary, effects on the colour of Lepidoptera. I believe that I 

 have now advanced a step further, and I have already expressed 

 my present and, as I hope, more correct and complete views on 

 these questions in one of my last writings,* relying on some of 

 these experiments. 



Had this not happened, I should have delayed the detailed 

 publication of the experiments for some years, as we have not 

 yet reached the end of the researches ; rather new questions 

 arise on the basis just won, which can only be answered by 

 further series of experiments. In the meantime I feel myself 

 obliged to bring forward illustrations of the experiments which 

 have already served for deductions. Nevertheless I cannot 

 neglect working at these questions again in the future, and more 

 completely revising the material. 



•'' Weismann, ' Das Keimplasma, eine Theorie der Vererbnng. Jena, 

 1892, p. 523, u. ff. 



