160 A. FRANKLIN SHULL AND SONIA LADOFF 



plasm, the suggested factor may be classed under nutrition. 

 But by so defining nutrition the term rnetabohsm becomes super- 

 fluous. Furthermore, it is clear from the context that none of 

 the writers just named meant anything more by nutrition than 

 quantity or quahty of food devoured. We care not about the 

 terminology, the ideas are distinct. 



SUMMARY 



The common effect of numerous substances upon the life 

 cycle of Hydatina senta (diminution of male-production) is 

 not due to their osmotic pressure, acidity or alkalinity, nor to 

 mere delay of certain processes. 



Calcium chloride, in very dilute solutions, repeatedly increased 

 male-production in one parthenogenetic line, not in another. 

 Magnesium chloride gave results that could not be interpreted, 

 while potassium sulfate, iron chloride, and ammonium chloride 

 all reduced male-production. Dilute bouillon also diminished 

 male-production. 



Oxygen in the water increases male-production. Its effect 

 is most marked in the counteraction of agencies which diminish 

 male-production, such as bouillon, manure solution, and creatin. 

 Whitney's experiments with Chalamydomonas, in which male- 

 production was greatly increased, an effect which he attributed 

 to nutrition, are partly explained, therefore, as dependent upon 

 the oxygen evolved in photosynthesis. Our results, however, 

 were not as marked as Whitney's, and experiments in which 

 the rotifers were reared with a green alga too large to be eaten, 

 gave negative results. It is probable that nutrition has some 

 effect, as Whitney supposed, but to what extent can not be known 

 until the other agents which can not be eliminated are separately 

 tested. 



