Published online by Cambridge University Press: 21 August 2001
The morphology of the cells during spermatogenesis in Amiantis umbonella (Mollusca: Bivalvia) was investigated from collections made between November 1997 and January 1999. Each stage is described and prominent features noted. The mature spermatozoan is primitive, lacking an apical rod, having a cylindrical-curved nucleus and a cone-like acrosomal complex bearing distally two swollen bulb-like terminals connected by thin, curved threads. Spermatozoa have a single flagellum and five (rarely six) mitochondria at the base of the nucleus.