The Influence of External Conditions 21 
in general that cooled or iced pup gave dark and much-spotted 
moths, while “forced” pupe were pale and spotless or with 
reduced spots. He states that the markings are affected by 
long-continued exposure, especially during the early pupal period, 
but the color is chiefly affected during the penultimate period. 
Standfuss has experimented on as many as 7000 individuals 
in all. He determined that the period in the life of the pupa 
when it is most sensitive to heat is at the beginning, although 
it is best not to try to produce the effect too soon after the cater- 
pillar has become a pupa. If exposed soon to extreme cold, the 
pupz die; but if exposed soon to heat the best results, z.e. the 
most divergent forms, are obtained, although the mortality is 
high. If the pupa is exposed as soon as it can stand it to 
extreme cold and then to heat, the heat-type is produced. In 
other words, the cold delays the development so that the heat 
produces the greater effect; for as soon as the temperature is 
raised the development goes forward rapidly. To get the best 
effect from cold, Standfuss found it advantageous to expose first 
to low temperatures, then for 5 to 10 days to moderate cold 
(11° to 14° C.), and lastly bring the pup to room temperature. 
In ‘his earlier work Fischer subjected the pup for several 
days to extreme temperatures of heat or of cold, but later he 
found it better to subject the pupz two or three times a day 
to the extreme temperatures during a period of 11 to 20 days. 
This method applies particularly to extreme temperatures. For 
a low temperature he used 0° C. or — 3° C. or even —8° to — 20° 
C. The high temperature was from 35° to 46°C. The more ex- 
treme the temperature that the pup will stand the greater the 
effect produced. Thus temperatures between 0° and — 20° gave 
greater effects than those between 0° and +10°. Tempera- 
tures of 42° to 46° gave more striking results than those of 35° 
to 41° C. 
The most important result obtained by Fischer was to show 
that the same aberrations are obtained by extreme heat and by 
extreme cold. The result may seem puzzling, but it must be re- 
membered that the coagulation of proteids, which is probably 
