71 
siderable changes were sometimes produced in the later pupal stages, 
when the insect, having passed the central period of inaction, which 
in winter pupee was of very lengthened duration, was developing 
towards the imago stage ; these were usually only changes in general 
colouring, and were quite considerable in S. d¢/unaria and SS. tetra- 
lunaria, also in Z. punctarta, in which species also the marginal 
blotches indicative of the summer pupa could be produced by 
exposure to a high temperature during the last few days of the 
pupal period, after very long exposure to cold. He had never 
found, however, that any effect on colouring or markings in any 
species had been produced after the colouring of the perfect insect 
had begun to show itself through the pupa-case. Extreme results 
had been rarely obtained by him unless where the exposure had been 
so long that a little more would have crippled or killed the insect, 
and in fact did cripple or kill a large proportion. Very marked effects, 
however, were often produced without any approach to crippling ; 
such effects in many species are invariably produced by an exposure 
short of that which endangered crippling. He had only obtained the 
very extreme results in a moderate percentage, say five per cent. of 
those operated on, and he gathered that the experience of Dr. Stand- 
fuss and Dr. Fischer, at least so far as their experiments had been 
published, was somewhat similar. ‘Their experience, however, had 
been much greater than his, as they had operated on a very much 
larger number of individuals. | He understood that Dr. Fischer was 
now obtaining a much larger percentage of results by improvements 
in the processes employed. 
Turning to the more philosophical bearing of these results, the fol- 
lowing views of Mr. A. G. Mayer, of Cambridge University, U.S.A., 
as given in a recent number of ‘‘ Psyche,” were read by Mr. 
Merrifield : 
‘“‘T know of only one experiment upon the effect of excess7ve heat 
upon Lepidoptera, and that was performed upon the pupze of Vanessa 
antiopa by Fischer (’95), who, it will be remembered, subjected them, 
when fresh, for three hours, and then daily for two to three hours to 
a temperature of 104° F. to 108° F., keeping them at all other times 
at 85° F. to go° F. The butterflies which issued resembled those 
which would have resulted from exposure to cold of 32° F. to 34° F. 
“It has occurred to me that in this remarkable fact we may have a 
clue to at least a partial explanation of the action of cold upon 
seasonally dimorphic Lepidoptera. It is well known, from the 
researches of Dutrochet, Rossbach, and Plateau, that if organisms be 
subjected to gradually increasing heat the metabolic processes as 
evinced by increased excretion in protoplasm, and more rapid rate of 
development, become more and more active, until suddenly all move- 
ments cease and heat rigor sets in. ‘This is not death, however, for 
if the organism be now cooled down, recovery takes place, and the 
life processes return with normal vigour. According to Plateau, the 
temperature of heat rigor in different insects varies between go° F, 
