AND OF LIGHT. 235 



times of emergence of the butterflies from the chrysa- 

 lis varied from 6 days to no less than 15 weeks, and 

 probably if the low temperature had been continued in 

 this latter case, the time would have extended to many 

 months, or there may have been no emergence at all. 

 It will be seen that the principal effects produced by 

 warmth are a dusky suffusion of the fore wings, and by 

 cold an intensity of colouring in both the coppery and 

 dark parts, the enlargement of the copper band on the 

 hind wings being an especially marked feature. In 

 fact these " cold " specimens were very similar to those 

 caught in England, Germany, and similar latitudes, 

 whereas the " warm " specimens were similar to the 

 variety eleus, which is found in Southern Europe. 

 Merrifield therefore came to the conclusion that the 

 difference in the appearance of these local forms " is 

 not necessarily to be attributed to the existence of races 

 of different colouring, but may be owing to the differ- 

 ence between the temperatures to which the individuals 

 are exposed in the two climates." Weismann has 

 shown,* however, that the modifications cannot be en- 

 tirely due to the direct effects of temperature. Thus 

 none of the specimens obtained by exposing pupse of a 

 German stock to high temperature were so dusted with 

 black as the darkest forms of the southern variety eleus, 

 whilst conversely, none of the specimens obtained by 

 exposing the pupse of a Neapolitan stock to a low tem- 

 perature were so light-coloured as the ordinary Ger- 

 man form. "The German and Neapolitan forms are 

 therefore constitutionally distinct, the former tending 

 much more strongly towards a pure reddish-gold, and 

 * " Germ-Plasm," p. 399. 



