VARIATION 



23 



diurnal peacock butterfly, Vanessa io, which show the fading out of the 

 "peacock eye" mark (see Fig. 5). 



(c) Food and Structure. Woltereck was able to prove that the form 



FIG. 6. The diurnal peacock-butterfly (Vanessa io), above, and below, forms produced 

 by subjecting the pupae to unusual temperatures. (After Goldschmidt.) 



(hence the structure) of the fresh water crustacean, Hyalodaphnia, varies 

 directly with the food supply. These minute animals produce many 

 generations during a season and the successive generations from the same 



3-VI 



28-VI 



18-X 



3-1 



30-VII 



15-IX 



FIG. 6. Morphological cycle of bead-height and shell-length in Hyalodaphnia. 

 numerals designate months. (After Woltereck, from Goldschmidt.) 



Roman 



water exhibit a morphological cycle, the earlier and later generations 

 having shorter heads and the generations produced from midsummer to 

 autumn having longer ones. Fig. 6 is a reproduction of Woltereck's 

 diagram of the morphological cycle in Hyalodaphnia showing variation 



