Presence of the Sperm Middle-Piece in the Fertilized Egg of the Mouse (Mus musculus)

Abstract

DURING an investigation of the cytoplasmic inclusions of the fertilized egg of the mouse, the sperm middle-piece, and in some cases the whole tail, was observed in the ooplasm (a and b). The middle-piece usually becomes detached from the sperm-head shortly after the entry of the sperm, but may remain attached until the stage of the pronuclei is reached. The middle-piece is, at first, compact and deeply stained, but soon shows a granular structure. These granules are identified as the mitochondria of the sheath of the axial filament (a, S.M.P.). After the middle-piece is free of the sperm-head the sheath becomes less compact, so that the individual granules can be identified with ease (b, S.M.P.).