230 



Heredity and Environment 



abnormal environmental conditions in early stages of ontogeny. 

 Effects of Food. In addition to such monsters, which are in- 

 capable of long life, many peculiar if not abnormal types of ani- 

 mals are produced by the action of unusual environmental stimuli 

 during later stages of development. Gudernatsch found that if 

 tadpoles of the frog were fed on the thyroid gland they trans- 

 formed into minute frogs, scarcely larger than flies, but if fed 

 on thymus gland they grew to be large, dark-colored tadpoles 



FIG. 83. YOUNG FISH. On the right a normal individual with two eyes ; 

 on the left Cyclopean monsters with one eye ; produced by treatment with 

 magnesium solutions. (From Stockard.) 



but did not change into frogs; if fed on the adrenal gland they 

 produced extremely light-colored forms. If canary birds are 

 fed on sweet red pepper they become red in color. If the larvae 

 of bees are fed on "royal jelly," which is a bee food rich in fats, 

 they become fertile females or queens; if fed on ordinary "bee 

 bread" they become infertile females or workers (Fig. 84). There 

 are marked structural differences between the workers and the 

 queens but the differences in their habits and instincts are even 

 more striking ; all of these differences whether in bodily structure 



