On a thin membrane formed in the perivitelline space during the early embryonic development of the horseshoe crab.

Abstract

A thin layer found in the perivitelline space of the horseshoe crab eggs was studied anatomically, histochemically and electron-microscopically. The layer exists from the stage of unfertilized egg to that of germ-disc formation. In the early stages it seems to be of only viscous structure containing mucopolysaccharide. However, in the late blastula stage, a thin membranous structure which can tear off by forceps appears on the outer surface of the layer. Accompanying with the swelling of the inner egg membrane, the viscous layer and the thin membranous structure are attached on the outer surface of the inner egg membrane, and then disappear. We propose a thin membrane in regard to all these structures.