The ultrastructure of the seminal vesicle, ejaculatory duct, cirrus sac and cirrus is described. The epithelium of the seminal vesicle consists of a single layer of squamous to cuboidal cells. The apical ends of the cells have thin polymorphic lamellae and long narrow pits, both of which enclose normal spermatozoa. The cells have a moderate amount of GER and Golgi complexes which produce a lucid secretory body. The ejaculatory duct epithelium is composed of cuboidal to columnar cells between or through which project the terminal parts of the ducts of the unicellular prostate glands. The apical surfaces of the epithelia are extended into triangular or filiform projections having thin sinuous lamellae. The cytoplasm contains GER cisternae and Golgi complexes which synthesize a dense ovoid secretion. The cirrus sac and cirrus are covered by a thin modified tegument. The cirrus has many spines and the normal ratio of T1 to T2 type of secretory bodies, whereas the cirrus sac has few spines and the T2 type of secretory body predominates over the T1 type. The significance and possible functions of the structures observed in the three tissues are discussed.