30 THE TESTIS AND ITS RELATION TO REPRODUCTION 



from the mammalian testis will not fertilize; those from the caudal portion 

 of the epididymis will, provided they have been in the epididymis long enough. 

 Under normal conditions sperm pass through the epididymis slowly, and retain 

 their viability after many days' residence in this structure. Sperm prove to be 

 fertile in the rabbit epididymis up to about the thirty-eighth day; if kept 

 somewhat longer than this, they become senile and lose the ability to fertilize, 

 although morphologically they may seem to be normal (Hammond and Asdell, 

 '26). In the rat, they may live up to 20 to 30 days in the epididymis and still 

 be capable of fertilization (Moore, '28). It has been estimated that the epi- 

 didymal journey in the guinea pig consumes about two weeks, although they 

 may live and retain their fertilizing power as long as 30 days in epididymides 

 which have been isolated by constriction (Moore and McGee, '28; Young, 

 '31; Young, '31b). It is said that in the bull, sperm within the epididymis 

 may live and be motile for two months. As a result of these facts, it may be 

 concluded that the epididymal journey normally is a slow process, and that 

 it is beneficial for the development of sperm "ripeness" or ability to fertilize. 



c. The Epididymis and Vas Deferens as Sperm-storage Organs 



Along with the maturing faculty, the epididymal duct and vas deferens also 

 act as sperm-storage organs. As observed on p. 23, in the bat, Myotis, sperm 

 are formed in great numbers in the seminiferous tubules and pass to the 

 epididymal duct where they are stored during the fall, winter, and early spring 

 months; the epididymal journey thus is greatly prolonged in this species. In 

 the ovoviviparous garter snake, Thamnophis radix, sperm are produced during 

 the summer months; they pass into the epididymides during early autumn and 

 are stored there during the fall and winter. In the mammal, sperm are stored 

 in the epididymal duct. 



Aside from its main purpose of transporting sperm to the exterior (see 

 sperm transport, p. 177), the caudal portion of the sperm duct or vas deferens 

 also is capable of storing sperm for considerable periods of time. In the 

 common perch, Perca flavescens, sperm are developed in the testes in the 

 autumn, pass gradually into the accessory reproductive ducts, and are stored 

 there for five or six months until the breeding season the following spring 

 (Turner, C. L., '19). Again, in mammals, the ampullary region of the vas 

 deferens appears to be a site for sperm storage. For example, the ampulla of 

 the bull sometimes is massaged through the rectal wall to obtain sperm for 

 artificial insemination. In this form sperm may be stored in the ampulla and 

 still be viable, for as long as three days. Similarly, in lower vertebrates large 

 numbers of sperm may be found in the posterior extremities of the vas deferens 

 during the breeding season. Thus, the reproductive duct (and its epididymal 

 portion when present) is instrumental in many vertebrate species as a tem- 

 porary storage place for the sperm. 



