The Effect of Testis Hormone on the Preservation of Sperm Life in the Vas Deferens of the Fowl

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Abstract
1. Mature sperm in the isolated ductus deferens of the fowl retain the capacity for movement in physiological saline for an average period of 26 or 28 days and a maximum of slightly more than 30 days, irrespective of the presence or absence of functional testicular tissue. Considering that sperm lose fertilizing ability before motility, this time accords closely with the reported survival of fertility in the hen after segregation from the cock. 2. While thus showing that testis hormone is not directly concerned with the maintenance of sperm life in the excurrent reproductive ducts of the fowl and suggesting that its positive effect in mammals is likewise indirect, it does not preclude the possibility that its action is expressed indirectly only through the epididymis. 3. The fact that the epididymis in the fowl is rather a vestigial organ and does not act as a storehouse for sperm makes it clear that in any case a physiologically controlled sperm-preserving mechanism plays no important role in the economy of reproduction in the fowl. 4. It is suggested that the nature of the demands made upon the supply of sperm in ducts of the males, as a consequence of the evolution of the sexual cycle in their respective females, satisfactorily accounts for the wide divergence in degree of epididymal development between Aves and Mammalia. Such demands, if in fact responsible for the divergence, have probably conferred advantages on well-equipped males and have most likely been produced through the agency of natural selection.