98 CAROLINE BURLING THOMPSON 



Wheeler ('07), writing on the polymorphism of ants, makes 

 a careful examination of the two opposed theories of the influence 

 of food upon organisms and of hereditary predetermination. 

 He draws attention to the tendency of the physiologist to study 

 an animal from the point of view of its reactions to external 

 stimuli, while an embryologist w^ould look rather for evidences 

 of predetermined differentiations, and he remarks, further, that 

 the embryologist has been at a serious disadvantage in his study 

 of the social Hymenoptera, in which, so far, no determining caste 

 characters have been detected in either the eggs or young larvae. 



On the question of the influence of larval food Wheeler states : 



Closer examination of the subject, however, cannot fail to show that 

 larval alimentation among such highly specialized animals as the social 

 insects .... is a subject of considerable complexity. In the 

 first place, it is evident that it is not the food administered that acts 

 as a stimulus, but the portion that is assimilated by the living tissues 



of the larva In the second place, while experiments on 



many organisms have shown that the quality of assimilated food may 

 produce great changes in size or stature, there is practically nothing 

 to show that even very great differences in the quality of the food can 

 bring about morphological differences of such magnitude as those 

 which separate the queens and workers of many ants. 



Wheeler next enumerates a number of concrete instances 

 tending to disprove the assumption that qualitative feeding 

 can produce morphological differences in the worker, but he 

 goes on to state that quantitative feeding may produce diminu- 

 tion of stature and some of the atypical phases found in ants. 



Such variations are of the fluctuating type and are therefore attrib- 

 utable to the direct effects of the environment. The sokUer and 

 worker, however, differ from the queen in the absence of certain char- 

 acters, like the wings, wing-muscles, spermatheca, some of the ovarian 

 tubules, etc., and the presence of other characters, like the peculiar 

 shape of the head and mandibles. In these respects the sterile castes 

 may be regarded as mutants, and Weismann's contention that such 

 characters cannot be produced by external conditions, such as feeding, 



is in full accord with de Vries's hypothesis It must be 



admitted that a direct causal connection between underfeeding on the 

 one hand and the ontogenetic loss or development of characters on 

 the other, has not been satisfactorily established. The conditions in 

 the termites, which are often cited as furnishing proof of this con- 

 nection, are even more complicated and obscure than those of the social 

 Hymenoptera. 



