Contiguous allografts of male and female gonadal primordia in the rat.

Male and femal gonadal primordia from fetal rats were grafted in contiguity under the kidney capsule of normal, castrated and spayed adult host rats. Irrespective of the gonadal status of the host, growth and differentiation of primary overian follicles were suppressed when a fetal testis was grafted close to a fetal ovary. Instead, cystic or tubular structures developed, some of them containing atretic ova in their lumina. The testis grafts, on the other hand, always differentiated extremely well. This is supportive evidence for the concept that the early fetal testis elaborates a substance or substances which are capable or preventing proper development of follicles in ovarian primordia trasplanted next to them.