while in otlier families the unconforming pupie were numerous 

 The pupse were often clustered together in little groups, and 

 individuals composing such clusters sometimes agreed with 

 each other in conforming or in not conforming. 



He did not propose on that occasion to discuss the general 

 proposition that the colour-resemblance was in these cases a 

 protection ; but he pointed out that if a larva had the power 

 of forming a green pupa when attached to a green plant the 

 conformity of colour would make the pupa less conspicuous 

 only so long as the plant remained green. In the case of the 

 summer brood of najn, for instance, this resemblance might 

 perhaps be effective, though in this case the pupal period was 

 very short, only two or three weeks. But in order that the 

 resemblance may benefit pupai which ovei'-winter it is necessary 

 that the green plant to which green pupee are attached should 

 remain green in the winter. His own pupae had turned green 

 on sevei-al food-plants which wither and go brown : in these 

 cases the puppe became conspicuous again. 



To form a sound judgment on this matter it would be 

 necessary to know how the pupae occur in nature. Pupae of 

 P. napi were hard to find. Had any one found the green 

 pupae in the wild state 1 



Prof. PouLTON wished to congratulate Mr. Merrifield on 

 the results he had obtained. He was particularly interested 

 to know that the pupie of F. machaon had now been proved 

 to be sensitive. His own experiments on the species led him 

 to infer the opposite, but they had been conducted with very 

 few individuals, and he had always hoped that the species 

 would be investigated on a large scale. 



The results obtained by Mr. Merrifield upon Pieris napi 

 were very striking and showed that the mature larvae were 

 most sensitive to the colours of their surroundings. The 

 strong influence of orange and yellow backgrounds in pro- 

 ducing green pupoi was corroborated by his own experience 

 and confirmed the conclusion reached in his earlier experi- 

 ments, that the efficiency of the greens of nature in producing 

 green pupae (and larvae) in sensitive species was due to the 

 orange and yellow rays which they reflect. 



He exhibited some pupae of Pieris hraadcoi which had been 



