158 A. FRANKLIN SHULL AND ■ SONIA LADOFF 



also periods of rapid growth, not all periods of rapid growth 

 are accompanied by many male-producers. And while lines 

 producing many males are usually vigorous hnes, there are 

 equally vigorous lines (judged by all known standards) that 

 produce comparatively few males. These facts may be har- 

 monized with the view that speed of reaction within the proto- 

 plasm makes for male-production, if we assume that only cer- 

 tain reactions bear this relation to sex. 



If we adopt the view that the rate at which certain chemical 

 events proceed determines the form of the hfe cycle, the posi- 

 tive results of our present experiments have some meaning. 

 The dilute solution of calcium chloride merely provides a medium 

 that is slightly more favorable to the processes concerned. 

 Oxygen obviously provides for accelerated oxidation in the 

 protoplasm. The effect of oxygen aside from male-production 

 is not merely inferred; for the rotifers in oxygenated water, and 

 those in Spirogyra cultures, were almost invariably healthier 

 than the control. Sometimes the families in the oxygenated 

 water were larger, but always the animals were more easily 

 reared to maturity. If qualitative differences of nutrition 

 affect the sex-ratio, as we must on the basis of Whitney's experi- 

 ments assume that they do, these may likewise be conceived 

 to affect the speed of the metabolic reactions. Even quantita- 

 tive differences of nutrition, should these eventually be found 

 to alter the sex-ratio, could conceivably alter the metabolic 

 processes; indeed, there are no a priori grounds for believing 

 that they do not. 



The suggestion that mere speed of reaction is responsible for 

 varying degrees of male-production becomes more plausible 

 if its operation can be visualized in terms of known processes. 

 It is well established, we believe, by the investigations of Shull 

 ('12, pp. 302-308), that male-production is either caused or 

 prevented at some time within the growth and maturation pe- 

 riod of every parthenogenetic egg. When an egg has passed its 

 maturation stages, the fate of the female which will hatch from 

 that egg is sealed. She will be either a male-producer or a 

 female-producer, according as one or another series of events 



