Food as a Sex-Determining Factor in Moina macrocopa

factor in the production of males by such mothers by Banta and Brown (1929a, 1929b). They ascribe the production of males by crowded mothers to the accumulation of the animals' own excretory substances. Stuart and Banta (1929, 1931); Stuart, Tallman, and Cooper (1931); and Stuart, Cooper, and Tallman (1931), however, showed that under certain experimental conditions available bacteria as food were an important factor in the production of males by crowded mothers. According to past findings then, these two factors-excretory substances and food-have been suggested as being associated with sex control in Cladocera. When two factors appear to be associated with a single phenomenon, the question naturally arises as to whether either factor alone can, under any conditions, cause the results ascribed to both. Evidence now available on this point is inconclusive, we feel, since most findings may be interpreted as supporting the r61e of excretory substances alone, or the r61e of food alone, or possibly a composite effect of the two. Thus it becomes quite evident that entirely new methods of procedure must be devised before either factor can be completely ruled out in any one experiment. The following experiments were designed to exclude the possible intervention of excretory substances in the control of sex in the offspring of Moina macrocopa mothers.