-Spermatogenesis in the southern Australian blindsnake Ramphotyphlops nigrescens is seasonal, with sperm production peaking in autumn, reduced in spring, and testicular recrudescence occurring from late spring to summer. Sperm is present in the epididymides from autumn to early summer. The retrocloacal sacs in this species do not function as sperm storage organs, contradicting the only previous hypothesis on the function of these structures. A peculiar feature of the testes of this species is the large size of the Sertoli cell nuclei, which are much larger than the spermatogenic cells. al of Herpetology, Vol. 35, No. 1, pp. 85-91, 2001 i ht 2001 Society for the Study of Amphibians and Reptiles atogenic Cycle, Sperm Storage, and Sertoli Cell Size in a hidian (Ramphotyphlops nigrescens) from Australia Scolecophidians are anatomically quite different from other snakes in a number of ways. Many of these modifications appear to be related to their burrowing lifestyle, along with a long independent history from the Alethinophidia (Robb, 1960; Robb and Smith, 1966; McDowell, 1974, 1987; Rage, 1987). In particular, the urogenital system shows peculiarities, at varying levels of generality among the families and genera. Among these are the presence of a median cloacal gland in typhlopids and leptotyphlopids (Robb, 1960, 1966a; Gabe and Saint-Girons, 1965; Fox, 1965), parthenogenesis in at least one typhlopid species (McDowell, 1974; Wynn et al., 1987; Ota et al., 1991), loss of the left oviduct in typhlopids and leptotyphlopids (Robb, 1960; Fox and Dessauer, 1962) and some anomalepids (Robb and Smith, 1966); and, in males, the segmented testes of typhlopids and leptotyphlopids (Fox, 1965) and the arrangement of mitochondria on the mature spermatozoon (Harding et al., 1995); and, in the Australopapuan typhlopid genera Acutotyphlops and Ramphotyphlops, a unique hemipeneal structure and the presence of retrocloacal sacs (Robb, 1960, 1966a,b; McDowell, 1974; Wallach, 1993, 1995). The retrocloacal sacs are unique and have been tentatively interpreted as sperm storage organs, although direct evidence for this is lacking (Robb, 1966b). idians are anatomically quite differother snakes in a number of ways. these modifications ap ear to be relateir burrowing lifestyle, along with a i ependent history from the Alethinophi( b, 1960; Rob and Smith, 1966; McDow4, 1987; Rage, 1987). In particular, the ital system shows peculiarit es, at varyels of generality among the families and . ong these are the presence of a mel acal gland in typhlopids and lepto yph( obb, 1960, 196 a; Gabe and Saint-Gi, 965; Fox, 1965), parthenogenesi in at In contrast to the attention paid to scolecophidian anatomy, there are few publications on ecology (Shine and Webb, 1990), especially the male reproductive cycle, for which there are only fragmentary data (Fox, 1965). This paper reports the first data on seasonality of the male gonadal cycle for an Australian typhlopid, Ramphotyphlops nigrescens (Gray, 1845), explores the possible function of the retrocloacal sacs in this species, and reports another unusual feature of the male genital system, the presence of large nuclei in the Sertoli cells of the seminiferous tu-