MALE-PRODUCTION IN HYDATINA 157 



by the green flagellates as a by-product of photosynthesis. 

 Our results show marked effects of oxygen. However, the in- 

 crease of male-production with oxygen alone is by no means 

 as great as Whitney obtained with Chlamydomonas. We sus- 

 pect, therefore, that although all the factors obviously associated 

 with Chlamydomonas in the cultures should be separately 

 tested before any residue of influence is assigned to nutrition, 

 Whitney's conclusion that the food conditions influence male- 

 production is correct, though that influence is less than he be- 

 Ueved. We are convinced, nevertheless, that this influence of 

 nutrition is dependent chiefly, if not wholly, upon quality, not quan- 

 tity, of food. Although large quantities of Chlamydomonas in 

 Whitney's cultures produced more marked results than small quan- 

 tities, this is to be attributed, we think, to the greater quantity 

 of oxygen evolved. It can not be assumed that am^ 'law of 

 mass action' holds for the ingestion of food by organisms. That 

 is, after a certain optimum (probably moderate) quantity is 

 reached, further 'concentration' of the food does not necessarily 

 increase the nutrition of the devouring animal. But such con- 

 centration of a green flagellate does increase the concentration 

 of oxygen in solution. If experiments with moderate quantities 

 of Chlamydomonas show an increase of male-production, it is 

 probable that such increase more nearly represents the effect 

 of nutrition itself. 



^ With the discoverj'- that oxygen increases male-production 

 are we any nearer a knowledge of the fundamental causes of 

 changes in the hfe cycle? We are inclined to answer in the 

 affirmative. It may be recalled that male-production is ordinar- 

 ily subject to marked periodicity (Mitchell, '13; Shull, '15). 

 Periods of many male-producers are also usually periods of 

 rapid growth and reproduction. Lines that yield many male- 

 producers are also usually vigorous. MetaboUc processes are 

 going on at a rapid rate. It is hard to avoid the suspicion that 

 in some way this speed of reaction in the protoplasm is related 

 to the production of males. Probably not all metaboUc proc- 

 esses, but only certain ones, are thus related to the sex-ratio. 

 For, while, as just stated, periods of male-production are usually 



