INFLUENCE OF ASSOCIATION ON THE SEXUAL PHASES OF GASTROPODS HAVING PROTANDRIC CONSECUTIVE SEXUALITY

¹ From the Osborn Zoölogical Laboratory, Yale University, and the Scripps Institution of Oceanography, University of California

1. The functional sexual phases of four species of Pacific coast gastropods with protandric consecutive sexuality have been investigated with regard to the conditions which control the change of sexual phase and particularly with respect to the influence of association or mating on the individual's sexuality.

2. In none of these species nor in six species previously studied is association a prerequisite for the development of the functional male phase, although isolation of these males after a prolonged mating period usually terminates the male phase promptly.

3. In nine of the ten species studied intimate association or permanent mating of the young male with one or more individuals in the female phase tends to accentuate the masculine characteristics and to postpone sexual transformation by prolonging the male phase. In five of these ten species the influence of association is very conspicuous; in four it is apparent but not conspicuous; in only one is the evidence inconclusive.

4. There seems to be no evidence that the accentuation and prolongation of the male phase by association is due to any masculinizing chemical secretion or hormone which passes through the water from the body of the female to that of the male, as some investigators have assumed; it seems more probable that stimuli received by the male through the sense organs in his penis and tentacles during association with the female are of such a nature as to influence his masculine characteristics, presumably by the mediation of hormones secreted within his own body.

5. Sexual maturity and sexual metamorphosis in these mollusks, like other types of metamorphosis in animals, are subject to environmental influences and can be accelerated, postponed or inhibited experimentally, but the sequence of sexual phases cannot be reversed.