1 8 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 pupae 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. 

 to 0° C. After this they were put three times daily for a short 

 period in a temperature of —3° for 18 days. They were then 

 kept in the cellar (14° C.) and finally at room temperature (22° C). 

 Six pupae 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 hygiaea; 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 pupae were brought into the extreme cold (three times 

 daily) for only 14 days. Five of these showed the aberration 

 artermis (like that in Fig. i, which developed, however, under 

 different conditions).^ The five individuals showed also aber- 

 rations with the hygiaea 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 pupae 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 0° and 6° C. 



