A critical analysis of excretory products as sex controlling agents in cladocera.

Conditions seem to exist under which the sex of the young to be produced by a Cladoceran mother is not determined by the animal's immediate environment. In such mothers a sex determining mechanism appears to have been inherited, and such mothers have been called "Sex Fast".Laboratory stock cultures of Cladocera not infrequently pass through periods of depression. While in such periods the mothers are for the most part "Sex Fast". Whether this can be termed sex control by inherent sexual cycles is questionable.The contention that many factors in the external environment of Cladocera may under suitable conditions act as sex controlling factors has been conclusively proven by numerous investigators. For the most part these are factors which affect the mother's metabolism, presumably accelerating or retarding the mother's development, acceleration being associated with female production, retardation with male production.Food, temperature and excretory substances are the external environmental factors most often associated with sex control in Cladocera. The evidence supporting the rôle of food and temperature in this reaction appears to be adequate but further experimental evidence supporting excretory substances in the control of sex is needed before a specific rôle in sex control in Cladocera can be assigned to this factor.