INDUCTION OF OOCYTE-NURSE CELL-DIFFERENTIATION IN THE OVARY BY THE BRAIN DURING THE INITIAL-STAGE OF OOGENESIS IN THE SILKWORM, BOMBYX-MORI(LEPIDOPTERA, BOMBYCIDAE)

Co-culture of ovarian cells in young larvae with brain induced meiosis and endomitosis of the silkworm, Bombyx mori. This suggests that a su bstance secreted by the brain controls meiosis and endomitosis. When p reparations from Bombyx heads were tested for meiosis inducing activit y, both the crude and highly purified preparations of bombyxin induced meiosis in vitro, but the crude preparation of prothoracicotropic hor mone (PTTH) showed much lower activity. This indicates that bombyxin i s the brain substance that induces meiosis. 20-Hydroxyecdysone also in duced meiosis, but only at a low concentration.