ABSTRACT
The nucleus is fusiform or clavate with the thin end anterior. In mature sperm the chromatin is seen to be condensed into medium-sized masses; scattered throughout the chromatin are lacunae which contain granules of varying size and opacity. A lateral implantation fossa (nuclear or centriolar fossa) is present near the anterior tip of the nucleus, which contains the proximal centriole at its anterior end and the distal centriole at its posterior end. The proximal centriole lies perpendicular to the long axis of the spermatozoon. The distal centriole forms the basal body of the axoneme, is separated from the nucleus by the anterior end of the axial fiber, and is orientated between 10-to 35Q to the long axis of the spermatozoon. The fossa is continuous with a longitudinal groove which extends for a short distance along the nucleus and which contains the axial fiber. The two centrioles and the anterior end of the axial fiber are enveloped in a granular and fibrillar material which is in contact with the slightly thickened nuclear membrane of the fossa and the groove. The chromatin consists of dense masses, irregular in size and distribution, separated by clear, granular zones.
