FACTORS INFLUENCING MOLTING AND THE SEXUAL CYCLES IN THE CRAYFISH

¹ Department of Zoology, Northwestern University

1. The phenomena of the delay in spring molt of egg-carrying females and of the changes in sexual form of males at the time of molt are described and illustrated by field observations on the crayfish, C. propinquus.

2. Removal of the eggs from the pleopods of egg-bearing females, C. propinquus, during the male spring-molting period results in an earlier onset of molting.

3. The delay in the spring molt of egg-carrying female crayfish, C. immunis and C. propinquus, is regulated by the action of the molt-inhibiting hormone of the sinus glands.

4. Various factors, that may operate to maintain the sinus gland activity until after the eggs hatch and the young leave the female, are discussed.

5. The changes in sexual form of male crayfish, C. immunis, at the time of spring and summer molts, and during winter molts induced by eyestalk extirpation are described.

6. Evidence is presented supporting an hypothesis that a male sex hormone, elaborated in the testes or other tissues, may regulate the cycle of changes in sexual form at the time of molt.