248 • CLAUDE W. MITCHELL 



It will be seen that these conclusions coincide with our own, 

 though in part only. The general emphasis upon nutrition is 

 the same. But Nussbaum places a much simpler construction 

 upon the facts than they will bear and in place of his conception 

 of simple starvation as the cause for male production we find 

 ourselves obliged to substitute the supposition of sporadic or inter- 

 rupted nutrition. Indeed our experiments show conclusively that 

 of the two aspects of this latter factor, the first or high feeding 

 is more important than the second or interruption by starvation. 

 The experiments upon which Nussbaum based his conclusions 

 consisted mainly of numerous mass cultures which were subjected 

 to quantitative variations in food supply. Many cultures were 

 carried simultaneously but definite controls were not made. 

 Shull has pointed out that Nussbaum's results are sometimes 

 contradictory, similar mass cultures producing or not producing 

 males. We believe however, that a closer study of the conditions 

 which Nussbaum has recorded for his experiments will sometimes 

 show that they were not uniform, and that, in the light of our 

 results, the contradictions disappear. It is unfortunately also 

 true that Nussbaum has not recorded the conditions of some of 

 his important experiments with sufficient fullness so that tlieir 

 real significance can now be determined. 



In brief resume, our analysis of the sixy-four experiments which 

 were really addressed by him to sex-determination, is as follows 

 — in some cases basing our judgment of the nutritive condition 

 upon Nussbaum's statement of the number of individuals present 

 and the number of eggs produced: Fourteen mass cultures, well 

 fed, then starved, produced males. Six mass cultures, well fed, 

 apparently not starved, produced males. Five cultures, con- 

 tinuously starved, produced no males. One culture, periodically 

 starved, produced no males. Twelve large mass cultures, ap- 

 parently well fed and without starvation, produced no males. 

 Thirteen small mass cultures, apparently well fed and not 

 starved, produced no males. Thirteen mass cultures, conditions 

 and nutritive supply not given or inferable from Nussbaum's 

 statements, produced males. 



