" It is likely that Mr. Marshall's observations are to be 

 explained by one or other of these alternatives." 



The President discussed Prof. Poulton's exhibit, and also 

 congratulated Mr. Marshall on the importance of his 

 discoveries. 



Mr. F, Merrifield read a paper, illustrated by a large 

 number of specimens, on " The Colouring of Pupse of P' 

 machaon and P. oiapi caused by the exposure to coloured 

 surroundings of the larvae preparing to pupate." 



It had generally been considered that the larva of P. 

 machaon was insusceptible to its surroundings when at the 

 period of pupation, but at the instance of Prof. Poulton he 

 had tried experiments last summer which proved that this was 

 not the case. Of eleven pupse of the first brood obtained in 

 July, six larvse were set to pupate on dark sticks ; four of 

 these were of the bone-coloured form, but a fifth was inter- 

 mediate and the sixth fell to the earth, where it formed a 

 green misshapen pupa. Of the five larvse set to pupate on 

 white sticks of peeled willow, four pupated on them and were 

 all green, the fifth pupated on the white muslin top and was 

 bone-coloured. Of seven other pupse that were found to have 

 attached themselves to the stems of the green carrot tops on 

 which they were fed, six were green and one bone-coloured. 

 This made a strong case, but experiments tried on a larger 

 number of the larvse of the second brood in September were 

 conclusive. Of 16 pupated on black paper or dark sticks, 

 all but one were bone-coloured, and most of them dark, four 

 that pupated on green carrot tops were all green, and of 19 

 others that pupated on yellow or orange all but one were 

 green. Various intermediate colours gave mixed results ; abso- 

 lute darkness produced five bone-coloured pupse but of a pale 

 hue. Seventy-two pupse had been obtained, and all these were 

 exhibited, as were the pupse or pupa-cases of the eleven of the 

 summer brood that had pupated. Several hundred pupse of 

 the second brood of P. najn were also exhibited, and these 

 were shown to be exceedingly sensitive. Of ten on black 



