542 A. FRANKLIN SHULL 



finds that the increased oxygen content of the water favors more 

 rapid multiphcation of these food organisms, and infers that the 

 rotifers were therefore better fed. That there is a certain low 

 concentration of food at which an increase of available food would 

 mean an increase of nutrition is probable. If food were in greater 

 concentration than this, it is not clear that further increase in the 

 amount of food at hand would cause an increase in the amount 

 eaten. A man who sits down alone at a table with a hundred 

 pounds of steak and fifty pounds of potatoes eats no more than 

 if only fifty pounds of steak and twenty-five pounds of potatoes 

 are set before him. 



If the above criticism is not valid, and it is after all merely 

 quantity of available food that determines male-production, 

 that fact should be very simply and easily discovered by controlled 

 experiments, involving large numbers of individuals, and the 

 next desirable step in the investigation is perfectly clear. 



The criticisms of Whitney's methods and conclusions in the 

 foregoing paragraphs may seem to indicate a wider divergence 

 between his conclusions and mine than really exists. Certainly 

 the conclusions reached in this paper and in that of Shull and 

 Ladoff differ less from Whitney's conclusions than Whitney's 

 recent article would lead one to suppose. Thus when Whitney 

 ('17, p. 114) writes "According to Shull and Ladoff, one would 

 expect many male-producing females to be produced in sunlight 

 and Chlamydomonas with the accompanying excess of oxygen, 

 but no male-producing females would be expected to be produced 

 in darkness and Chlamydomonas with no excess of oxygen," 

 he overdraws the indictment somewhat. The quoted statement 

 could be correct only if Shull and Ladoff had denied that food 

 had any effect on male-production, and had asserted that all 

 of the increase of male-production obtained by Whitney was due 

 to oxj'gen instead of food. No such idea was even suggested. 

 Indeed, there are frequent passages in the paper of Shull and 

 Ladoff that indicate the reverse. Thus on page 138 it is stated 

 "our results may be interpreted as being largely in support of 

 Whitney's contention." Again, page 156, 'part of the increased 

 male-prcduction following the use of Chlamydomonas as food 



