ABSTRACT
It is generally believed that the diapausing egg of the silkworm contains a substance which is transmitted from the mother and has an inhibitory action upon the development of the embryo. Watanabe (1924) was the first author to explain the phenomenon of diapause in the silkworm egg by postulating this substance which he called ‘inhibitory substance’, and almost all subsequent authors in Japan have accepted this assumption. It is not unreasonable to suppose that the ‘inhibitory substance’, which reveals its action in the egg after deposition, has some connexion with the diapause factor (hormone) secreted by the suboesophageal ganglion of the mother (Hasegawa, 1951, 1952; Fukuda, 1951), but nothing is known about the real nature and action of the diapause factor (Fukuda, 1955).
