12 THE EVOLUTION OF 



the direct influence of temperature. That, however, such diffe- 

 rences might not, without a direct influence, under special 

 conditions act as a stimulus to change of colour, 1 also feel 

 bound to contest. Every where, even out of the boundaries 

 of animal life, evolutions show the phenomenon of gene- 

 pistasy and the excitement there from by internal or external 

 influences acting as a stimulus. How strongly this pheno- 

 menon — which in a former study on the process of atrophy 

 of the horn of Sphingidae-caterpillars I indicated clearly — 

 shows itself in the course of colour-evolution in butterflies 

 and their caterpillars, is to me quite an undoubted fact. 

 That stimulating influences must act thereupon seems a 

 necessary consequence; and why should those influences of 

 temperature not be able to have that effect? 



Of very little meaning — though I have to mention it 

 here also by the way — is, with regard to the topics of 

 my studies, Mr. Roland Trimen's recent speech on seasonal 

 dimorphism in Lepidoptera ') as it contains simply a report 

 of work done by others, but no new views. I think, how- 

 ever, he might have mentioned something of what I com- 

 municated concerning his special subject, if only (for comple- 

 teness' sake) my observations concerning Cyllo Leda L. made 

 in Java, the more so, as I presented a copy of my paper to the 

 Entomological Society of London. It struck me also that Dr. 

 Dixey still considers Catopsilia Crocale Cram, and C. Po- 

 mona F. including C. Catilla Cram, as seasonal forms of one 

 species which Mr. de Niceville thinks doubtful, all the 

 supposed distinctive characters proving quite inconstant and 

 breaking down when large numbers of specimens are com- 

 pared. Even as far back as 1890 I published — though in 

 French ^) — such ample statements about this peregrina- 

 ting butterfly that its identity cannot leave any doubt 



1) Proceedings of the Entomological Society of London, 1898. 



2) Observations sur des vols de Lepidoptères aux Indes-Orientales Neerlan- 

 daises et considerations sur la nature probable de ce phenomcne (Natuurkundig 

 Tijdschrift voor Ned.-Indië, Dl. L). 



Notes iroin the L.eyden Museum, Vol. XXH. 



