Foetal testes control the prenatal growth and differentiation of the gubernacular cones in rabbits--a tribute to the late Professor Alfred Jost.

Gubernacular cones develop during foetal life in males of various species, including many of the common small laboratory animals. Postnatally these papilla-like organs invert and develop into the muscular cremaster sacs, providing space for testis descent. The mechanism governing male-specific development of these structures during foetal and postnatal life is unknown but foetal testicular androgens or anti-Müllerian hormone are unlikely to be involved. The present study of gubernacular cone development in 28-day-old rabbit foetuses castrated 5-9 days before questions whether foetal testis hormones play any role in these developmental processes. The study comprised an analysis of the microscopic slides in the legacy of the late Professor Alfred Jost in Paris. Castration at an earlier (19 days) or later (23/24 days) day of foetal life interfered with gubernacular cone growth and differentiation. Unilateral castration partially inhibited ipsilateral gubernacular cone growth. Implantation of a foetal testis close to the ovary could induce male-type gubernacular cone growth in females. Together the data unequivocally support the concept of foetal testicular hormonal control of male-specific gubernacular cone development. Further study is required to unravel the nature of the active foetal testicular agent.