8 



rendered black-spotted and gi'een by black and yellow sur- 

 roundings respectively, and a few pupa? of Papilio podalirius 

 which seemed to indicate that that species was sensitive. In 

 some experiments which he had conducted during the past 

 summer upon the struggle for existence in pup?e, very large 

 numbers of pupje of Vanessa xirticce were produced upon back- 

 grounds of various colours, with results which confirmed 

 the conclusions he had already recorded. He hoped soon to 

 bring a detailed account of these observations upon pupal 

 colour-adaptation before the Society. 



Replying to Mr. Bateson's objections to the interpretation 

 of the colour-susceptibility of the pupje of Pieris napi as of 

 protective value, he considered that it was in every way 

 probable that the larvse wandered before pupation (as those 

 of allied species were known to do) and that their power of 

 becoming green was of value when they were fixed to grasses 

 or other plants which remain green through the winter. 

 Even if all such green surfaces were covered up with snow in 

 the more northern part of the I'ange of the species, this would 

 not be the case for the whole of the winter pupal period, nor 

 would it hold good for other parts of the range. As to the 

 objection that the results obtained with bi'ed pupje were not 

 invariably consistent, in his experience the more completely 

 the experiment was conducted with this sole object in view, 

 the more uniform and convincing was the result. 



Furthermore, the conditions of even the most carefully 

 conducted experiments differed in many respects from those 

 which obtained in nature. The proof required by those who 

 objected to an interpretation based on natural selection was 

 the discovery in nature of the exceptions noted in their 

 experiments — that of light green pupas of P. napi or P. rapes 

 or the golden or green pupae of Yanessce upon grey stone, or 

 the dark forms of all these upon leaves. 



Although soDie of these pupse had been often observed in 

 one or both situations he had not heard of any single ex- 

 ception to the rule ; and if they occurred they must be 

 excessively rare. 



