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 
Fic. 5.—The diurnal peacock-butterfly (Vanessa io), above, and below, forms produced 
by subjecting the pups# 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 31 
28-VI nes 
30-VII ee 
Fic. 6.—Morphological cycle of head-height and shell-length in Hyalodaphnia. Roman 
numerals designate months. (After Woltereck, from Goldschmidt.) 
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 
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