130 A. FRANKLIN SHULL AND SONIA LADOFF 



Acidity 



In one of Shull's ('11) earlier experiments it was found that 

 sodium hydroxide reduced the proportion of male-producers 

 to a slight extent. At the same time experiments with acids 

 were performed in the hope of obtaining the opposite effect, 

 but it was found impossible to rear the rotifers in even a very 

 dilute solution of the inorganic acids used. Although weak 

 solutions of hydrochloric acid were used, by the time the sHghtly 

 alkahne food was added, the solution appeared neutral. When 

 he used solutions of the acid strong enough to remain acid after 

 the food was added, the rotifers died. 



With the expectation that organic acids might be less deleteri- 

 ous, the following experiment with butyric acid was begun. 



Experiment ^. A 1 per cent stock solution of butyric acid was kept 

 in a glass stoppered bottle, and diluted for use to 0.03 per cent (the 

 diluent being Great Bear spring water). Two lines of rotifers derived 

 from two sisters isolated September 10, 1911, were reared, one in spring 

 water, the other in butyric acid solution. For want of a satisfactory 

 indicator, it was not known that the latter solution remained acid 

 after the food was added. The characteristic odor of butyric acid 

 remained, but it was to be expected that the buty rates would possess 

 the same odor. 



Contrary to our hopes, the acid reduced^ the proportion of 

 male-producers, as shown in table 2. 



Delay or inhibition by manure solution 



The non-occurrence of male-producers while the rotifers were 

 being reared in strong manure solution might be attributed 

 to delay, rather than to inhibition. So long as a line were reared 

 continuously in manure solution the delay would be continuous; 

 but if only one or two generations were reared in such a solu- 

 tion, might not male-production which could not occur in these 



* It may be pointed out that the families are larger in butyric acid (mean size, 

 47.1 daughters) than in spring water (mean size, 38.7 daughters). According to 

 Mitchell's conclusions ('13) based on Asplanchna but applied to rotifiers in gen- 

 eral, the higher nutrition evidenced by larger families should have been accom- 

 panied by greater male-production, instead of less. 



