( ccs) 
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 nap, 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 pupze which over-winter it is necessary 
that the green plant to which green pupe are attached should 
remain green in the winter. His own pupe had turned green 
on several food-plants which wither and go brown: in these 
cases the pupze became conspicuous again. 
To form a sound judgment on this matter it would be 
necessary to know how the pup occur in nature. Pupz of 
P. napi were hard to find. Had any one found the green 
pup in the wild state? 
Prof. Pouuron wished to congratulate Mr. Merrifield on 
the results he had obtained. He was particularly interested 
to know that the pupe of 2. 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 larve were 
most sensitive to the colours of their surroundings. The 
strong influence of orange and yellow backgrounds in pro- 
ducing green pup 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 pupe (and larvee) in sensitive species was due to the 
orange and yellow rays which they reflect. 
He exhibited some pupe of Pieris brassice which had been 
rendered black-spotted and green by black and yellow sur- 
roundings respectively, anda few pup of Papilio podalirius 
which seemed to indicate that that species was sensitive. In 
some experiments which he had conducted during the past 
