[Fusion of the ventricular walls at the level of the dorsal and ventral telodiencephalic sulci].

In the course of development of the mouse embryo prosencephalon, the walls of the dorsal and ventral telodiencephalic sulci fuse along their ependymal surfaces. This study is based on 1 mu semithin sections of the prosencephalon and on ultrathin sections of the fusion zone of mice of 13 days postconception. Ultrathin sections of the rostral part of the fusion zone present two rows of junctions (maculae adhaerentes) in opposition belonging to each of the two walls. On either side of these rows of junctions is found a row of cells, many in various stages of mitosis. In the caudal part of the fusion zone, intercellular spaces are wide and are occupied by numerous cytoplasmic prolongations that present mitochondria, granular endoplasmic reticula, and Golgi apparatus. Many of these prolongations establish contacts between themselves and with the cell bodies.