DEPARTMENT OF GENETICS. 



101 



" In general, the experiments point to excretory products as probable causa- 

 tive factors in male production. Pressure may really serve merely to prevent 

 volatilization of certain excretory products. But lacking ready means for 

 determining the various excretory products and their relative amounts, 

 produced in such small animals as Cladocera, it is obviously difficult to 

 imitate and thus artificially bring about a situation duphcating that which 



develops in a 'crowded' bottle of these animals. Hence, if we are to formu- 

 late the hypothesis that the accumulation of excretory products is a large 

 factor in male production, it is exceedingly difficult to bring about a treat- 

 ment which will test the hypothesis. We have tested many combinations 

 (though by no means all the possible combinations) of the presumed excretory 

 products with only indifferent and inconclusive results sO far. 



"The conclusion would seem to be that the conditions favoring male pro- 

 duction are quite comphcated, that excretory products probably constitute 

 a large factor, that there is a delicate balance which, if much disturbed, as 

 by most of our treatments, results in a reduction in male production, but 

 that any treatment which materially affects male production throws hght 

 on the situation involved and promotes the analysis correspondingly. 



"To summarize the treatments catalogued in the table, aeration by what- 

 ever method, changes of whatever nature in the food, treatment with many 



