The origin and formation of the spermatozoa and spermatophore in the penaeid prawn Penaeus indicus has been described. Spermatogenesis takes place in the lumen of the testicular acini which have a peripheral germinal zone. Spermatogenesis involves the progressive reduction of the cytoplasm to produce a spherical sperm having an electron dense cap region containing the acrosomal complex from which extends a single spike. Histochemical studies revealed that the spermatozoa had a remarkable abundance of polysaccharides and basic proteins such as arginine and lysine, but was poor in lipids. Spermatophore formation took place inside the vas-deferens with the aid of seoetory epithelial cells lining the ducts. The mid vas-deferens was responsible for the deposition of the spenn matrix, spermatophore layer I and the wing, while the distal was deferens secreted the outer bounding layer (Layer II). The terminal ampoule served to mould the spermatophore into its characteristic oval shape and for its forceful ejaculation (luring copulation. The complete spermatophore was electroejaculated and its structural morphology and chemical composition of the acelluar bounding layers was studied.