Function of the Brain through Nerve Commissures on the Suboesophageal Ganglion in Bombyx mori L.

Abstract

Fukuda and Hasegawa have verified^1–3 that voltinism in the silkworm is probably controlled by a hormone from the suboesophageal ganglion. Hasegawa has claimed that voltinism may be determined by the function of the suboesophageal ganglion alone, while Fukuda has assumed that it may be determined by that of the brain-suboesophageal ganglion complex at the pupal stage. It can be inferred from Fukuda's experiments that the brain controls the secretion of the suboesophageal ganglion. When the brain completely suppresses the secretion of the suboesophageal ganglion, the silkworm moths lay batches of non-diapausing eggs. When the brain accelerates the secretion of the suboesophageal ganglion, on the other hand, the moths lay batches of diapausing eggs. Fukuda concluded that the centre which controls voltinism lies in the pupal brain. Morohoshi⁴ later recognized that inhibitory and accelerating functions of the brain are not completely absent but act only weakly.