18 Experimental Zoology 
show how the broadening of the yellow margin begins in the 
posterior wings and finally extends forward to the same extent 
on the anterior wings. The change is in an antero-posterior 
direction. The conditions under which these butterflies had 
been kept were as follows :— 
In the first experiment 20 pupe of Vanessa antiopa, about 
12 hours old, were kept for six hours at a temperature of 14°C. 
and then four hours in a temperature decreasing from 14° C. 
too° C. After this they were put three times daily for a short 
period in a temperature of —3° for 18 days. They were then 
keptin the cellar (14°C.) and finally at room temperature (22°C.). 
Six pupe died, the remaining 14 began to emerge after 10 to 12 
days. Figure 7 shows one of these butterflies which is the 
aberration known as hygiza; another is shown in Fig. 6, in 
which the blue spots and the dark border have completely dis- 
appeared, but the yellow border does not extend inward so far 
as in the last case. Three other individuals (Figs. 2, 3, 4, 5) 
show transitional forms in some of which traces of the blue 
spots could be seen. The last butterfly of this series to emerge 
was like the normal antiopa with the blue spots even larger 
than the normal, but less sharply defined. Thus under identi- 
cal external conditions quite a range of colors result; but of 
course the caterpillars themselves had probably not lived under 
identical conditions, nor had they been subjected to the cold at 
precisely the same stage in their pupation. 
In a second experiment the conditions were the same, except 
that the pupz were brought into the extreme cold (three times 
daily) for only 14 days. Five of these showed the aberration 
artermis (like that in Fig. 1, which developed, however, under 
different conditions). The five individuals showed also aber- 
rations with the hygiza characters. Two individuals were like 
Fig. 4; the others were like the intermediate forms. 
In a third experiment the conditions were the same as before, 
except that the pupz were brought into the extreme cold for 
only six days. They produced one normal butterfly; one transi- 
? The butterfly had been kept at a temperature below o° and 6° C. 
