A consistent feature of epithelial cells lining the initial segment of the ductus epididymidis of rats bilaterally castrated for about three months is the presence of stacks of annulated lamellae. They were occasionally observed by two months following gonadectomy but were not evident in one-month castrates nor in normal controls or unilaterally orchiectomized rats.

Observation of epididymides from neonatal and fetal rats taken at daily intervals between the twelfth and twenty-first day following conception demonstrated that small and inconspicuous annulated lamellae occurred normally during differentiation. They were observed on several occasions in widely scattered cells during the fifteenth day of gestation.

In the epididymis, annulated membranes may form from the outer nuclear membrane by a process of budding. The annulated membrane complex is “destroyed” in long term castrates following the subcutaneous injection of testosterone proprionate.