Perionyx excavatus (Oligochaeta) is a vermicomposting earthworm of which the reproductive strategies are little known. In order to obtain more information on this, its reproductive systems were studied. Existing literature on the topic is either contradictory or scant. The investigation was done by examining the gross anatomy and histology, using scanning and transmission electron microscopy_ The male reproductive system consists of two pairs of testes in segments 10 and 11 and two pairs of seminal vesicles in segments 11 and 12. In mature worms the developing spermatozoa are released by the testis into the body cavities of segments 10 and 11. The seminal vesicles in a particular segment receive developing spermatozoa from the lumen of the preceding segment. Two pairs of ciliated sperm funnels also occur in segments 10 and 11 and become the ciliated vasa deferentia carrying the sperm. The vasa deferentia on each side fuse to form only one vas deferens. These vasa deferentia reach the pair of prostatic glands in segment 18, each joining the prostatic duct and opening via the ventral male openings adjacent to each other on segment 18. Associated with the male openings are retractable penial chaetae. The cellular composition and organelle distribution of some organs and structures are also described. The positions of the female reproductive structures are illustrated diagrammatically in this paper.S. Afr. J. Zool. 1997,32(3
