1. In the viviparous roach, Diploptera, the factors controlling the maturation of the eggs were studied during an interval encompassing the first pre-oviposition, first pregnancy, and second pre-oviposition periods. During egg maturation the corpora allata become active as judged by histological criteria (increase of cytoplasmic content); they become and stay inactive during pregnancy. Ovarian inactivity after allatectomy also demonstrates that active corpora allata are responsible for the deposition of yolk in the oocytes. In addition, the corpora allata control the activity of the accessory sex glands, and of an as yet unknown type of cell presumably located in the bursa copulatrix, the secretion of which facilitates the extrusion of the spermatophore.2. In virgins, the brain inhibits the function of the corpora allata by way of the nervi corporis allati, and thus prevents or delays the maturation of the eggs. Severance of these nerves results in a sustained activity of the corpora allata with the resul...