254 KELLOGG AND BELL 



slightly larger standard deviation and hence coefficient of vari- 

 ability than the females. 



Although mosquitoes are insects with complete metamorpho- 

 sis, in which the adult (imaginal) external structures are dis- 

 tinct from the larval, and appear at once, on the issuance of the 

 adult from the pupal cuticle, in definitive condition, size of 

 wings, as well as size of other parts of the body, is a character 

 which may probably be influenced by the successful or faulty 

 food getting of the metabolism of the larva, and thus be really 

 in some degree an acquired variation instead of a strictly con- 

 genital one. In this particular instance the conditions of larval 

 life were apparently as nearly as possible identical for all the 

 larvae of these studied adults ; all the larvae lived at the same 

 time period in the same small pool. This identity of environ- 

 ment and life-conditions must have caused, to the extent that 

 environment can cause, the same variations to be acquired by 

 all the individuals, so that the lot should really show no differ- 

 ence (among its members) due to environmental influence. 

 Any variation inside the lot ought, therefore, to be blastogenic 

 in character. These blastogenic variations simply unfold and 

 develop during the development of the individuals, remaining 

 as unaltered in their relation to each other as they were in the 

 egg, but, of course, now magnified to visibility by the very 

 process of development. It should be noted in this connection 

 that while nature or the experimenter may offer to a given lot 

 of developing individuals identical amounts of food, under 

 identical conditions of light, temperature, etc., there may be 

 some individuals incapable of assimilating what is the optimum 

 or minimum amount for others so that in so far as quantity of 

 food constitutes environment and makes for development, these 

 delicate individuals will not get their share. The experimenter 

 can only work into the insect what the insect will accept, and 

 only that part which the insect adopts may correctly be called 

 his environment. We have bred silkworms which always had 

 left-over scraps after each meal, while their neighbors left never 

 a scrap ; also larvae which seemed destined to fail at moulting 

 or pupating or issuing. Faulty metabolism and faulty food 

 getting may occur under the best of environment, but, such 



