Postnatal development of seminiferous tubules in the cat.

Testes were obtained from 20 cats with an age range of 1 day to 1 year. In the neonatal period the seminiferous tubules were widely separated by a well-developed interstitium. Tubular diameter was small and no lumen was observed within the seminiferous tubules. These showed many undifferentiated Sertoli cells with round to ovoid nuclei and only one or two spermatogonia, usually centrally situated. From 2 to 4-5 months the interstitium was sparse, tubular diameters were increased and the morphology of the seminiferous tubules was very similar to that in the neonatal period (< 2 months). From 5 to 7 months, tubular diameters were larger, a lumen was observed, the seminiferous epithelium began to assume its characteristic stratification and the blood testis barrier was developed. From 8 months of age spermatogenesis was fully established.