ABSTRACT
The role of food and metabolic products in the control of sex in Cladocera has received considerable attention in the last one or two decades. Practically all the evidence favouring excretory substances as sex-controlling agents has been derived from the fact that crowded mothers produce a much higher percentage of male young than isolated mothers. It is self-evident that crowding Cladocera must favour the accumulation of metabolic products, but the results of crowding cannot be confined solely to the accumulation of the animals’ waste products. Food must also be considered as contributing to any effects that the crowding may have on the sex of the young produced by crowded mothers. The work of Woltereck (1911), Tauson (1930), Stuart and co-workers (1929, 1931 a, b, c, d, 1932 a, b) and numerous others on food has led many investigators to conclude that, of the two factors in question, food is the more important sex-controlling agent under ordinary conditions.
