ENDOCRINOLOGICAL STUDIES ON SPERMATOGENESIS IN THE SILKWORM, BOMBYX MORI L.

When embryonic testes 1 or 2 days before hatching were transplanted into 5 kinds of hosts (5th instar larvae, “fresh” pupae just after pupation, isolated pupal abdomens and 3-day-old pupae with and without their original corpora allata), the testes transplanted into 5th instar larvae grew most conspicuously and spermiogenesis began in many cysts. A few spermatidal cysts were observed in the testes transplanted into fresh pupae. No signs of maturation were observed in the testes transplanted into other hosts. It is concluded that prothoracic gland hormone might be responsible for the precocious maturation of young testes. On the other hand, the initiation of spermiogenesis was delayed, in comparing with controls, in the 3rd instar larval testes as follows: the testes transplanted into 3-day-old pupae, the testes transplanted into isolated pupal abdomens together with adult corpora allata and the testis into which corpus allatum of a 3rd instar larva was inserted. It is concluded that corpora allata hormone exerts an inhibitory effect on spermatogenesis.