DIFFERENTIATION OF GRAFTED WING-GERMS 473 



large quantity of blood during the operation, we can readily 

 understand that they might have been much weakened by the 

 operation and have responded more readily to all changes of 

 external conditions, such as temperature, moisture, etc., even 

 when these were imperceptible to us. In contrast to L\^nantria 

 dispar, Cosmotriche potatoria belongs to those species of moths 

 whose dimorphic wing-colors undergo distinct changes under the 

 influence of cold; to this difference Prell ascribed his results, 

 which he considers different. The later investigations of Prell 

 ('lob) on the castration of various Vanessae, the classical 

 material for the study of the influence of temperature, do not 

 seem to support this opinion. Castrated Vanessae as well as 

 castrated females of Cosmotriche potatoria undergo no changes 

 after castration, in contrast to males of the latter species. In 

 this behavior of the Vanessae, Prell ('15 b) sees a proof that in 

 the experiments on males of Cosmotriche the change in hue was 

 not excited by the operation itself, but that we have here to do 

 with the effect of the removal of the sexual glands; for if the 

 lighter hue of the wings of the males of| Cosmotriche were to 

 depend on the operation itself, it would have to be admitted, 

 according to Prell, that similar changes would appear also among 

 the Vanessae operated upon, as they are even more sensitive to 

 the influence of external conditions. I believe, however, that we 

 might just as well suppose a different reaction power of the 

 moth to castration, possibly different in the two sexes or in various 

 forms of moths, as a different behavior of various organisms, in 

 respect to their change of color, affected by debility and super- 

 sensitivity resulting from the operation. In this way the results 

 obtained by Prell may be made to accord with the results of the 

 researches of Oudemans, Kellogg, Meisenheimer, and of my own. 

 AATiile some authors have seen certain contradictions in the 

 results of different investigations, which, according to them, prove 

 the influence of castration on the dimorphism of the moth, 

 others have drawn the conclusion, from all these experiments, 

 that the germ of the wings is already differentiated early in the 

 larval life, and hence the removal of the gonad or the implanta- 

 tion of glands of the other sex cannot change anything in the 



