STUDIES ON THE SEXUAL ORGANIZATION OF THE RIHZOCEPHALA. III. THE MODE OF SEX-DETERMINATION IN PELTOGASTERELLA

Abstract

Adult females of Peltogasterella gracilis (syn. P socialis) occur gregariously on a single host-crab. Usually, females on 1 host produce eggs of 1 type[long dash]either large or small. The large eggs (160-175 [mu] in diameter) develop into large larvae which function as larval (cypris) males. The smaller eggs (140-150[mu] in diameter), on the other hand, develop into small larvae which give rise to adult females. No discernible structural difference is detected between the large-egg-producing females and the small-egg-producing females. In the meta-phase plate of the 1st maturation division of the large egg, 15 bivalent chromosomes are seen; while in the small egg a univalent chromosome is found beside 15 bivalent chromosomes. This univalent chromosome behaves like a sex-chromosome at the late stage of the first maturation division anaphase, but its exact nature is unknown.