Sperm dimorphism, in which both fertile 'eusperm' and sterile 'parasperm' are produced in the testis, has been implicated in sperm competition in insects and snails.  Parasperm are unique cells that usually lack an acrosome, eliminate the nucleus by a process akin to apoptosis (programmed cell death) and develop a complex cytolpasm swollen with secretions.  Previous work on Fustitriton oregonensis has documented the genesis of lancet parasperm, the ultrastructural hallmarks of apoptotic nuclear breakdown and the glycoprotein nature of the cytoplasmic granules.  The current study focuses on paraspermatogenesis, the confirmation of apoptosis and the characterization of cytoplasmic secretions of lancet parasperm of Ceratostoma foliatum, the Leafy Hornmouth.  This large whelk, abundant along Canada's West Coast, is a potentila model animal for studying these processes in detail.  Ripe testis were fixed for light and electron microscopy using standard protocols. A Promega kit, for detecting 3'-OH DNA overhangs that characterize apoptosis, was applied to testis squash preparations on CellTak™ (BD Biosciences) coated slides.  Percoll gradients were used to isolate parasperm from eusperm; subsequently the proteins they contained were characterized by lysing purified fractions and running electrophoresis on polyacrylimide gels.  The process of nuclear breakdown in the lancet of C. foliatum follows the hallmarks of apoptosis in ultrastructure as well as in the presence of 3'-OH overhangs, thus implicating parasperm as models in elucidating the nuclear events of apoptosis.  C. foliatum lancets are similar biochemically and structurally to other lancets and may be important in distinguishing between terminal taxa.