ON THE DEVELOPMENT OF THE TESTIS OF THE HORSE

The aim of the study was to answer the open questions concerning the d evelopment of the horse's testis. This study revealed that the seminif erous tubules originate from the sex cords of the coelomic epithelium and Leydig cells fi-om the proximal part of mesonephric nephrones, whe reas the rete and the ductuli efferentes derive from intermediate and distal parts of the mesonephric tubules. During the development the Le ydig cells undergo an enormous proliferation due to the PMSG secretion in the mare. The proliferation of these cells prevent the deep penetr ation of the rete into the medulla and is therefore the reason for the reduced extension of the rete and mediastinum testis in the stallion, although 80% of these cells degenerate in the last third of pregnancy . The growth of the seminiferous tubules during sexual maturity reduce s the rete to the extremitas capitata of the testis.