Copulation involving hypodermic impregnation is described for Elysia patina Marcus and E. subornata Verrill (= E. cauze Marcus) (Mollusca: Opisthobranchia: Ascoglossa). ln E. patina copulation may involve more than two animals and sperm is delivered into distinct globular structures, called ‘gametolytic vesicles’ in the original description of the species. The penis of E. patina is armed with a short cuticular style. The spermatozoa are of the ‘advanced’ opisthobranch type with no visible acro- some, an elongate head, a spirally coiled middle section showing a mucopolysaccharide coating, and a straight tail section. In E. subornata copulation involves only two animals in the usual position with anterior right sides opposing. The penis is unarmed, and sperm is delivered into the subepidermal tissues, forming irregular white ‘spots’ after copulation. Previously copulation in ascoglossans with only two genital openings was thought to involve insertion of the penis through the oviducal opening, but this has never been observed. Also, penial armature is not necessary for the successful application of hypodermic impregnation.