REPRODUCTION 47 



most favorable conditions. A normal alkaline solution 

 in the uterus is the most favorable medium for the long 

 continued vitality of the sperm-cells. It is very often 

 the case that the secretions in the reproductive organs 

 of the mare are acid and such a chemical condition is very 

 unfavorable to the continuance of the life of the sperm. 

 It is true that the sperm-cells will live but a few hours 

 in such an acid medium as is sometimes found in the 

 uterus. A study of the literature on the longevity of 

 the sperm-cells in the female reproductive organs is 

 somewhat confusing. It is probable that very consider- 

 able differences exist in the vitality of the spermatozoa 

 from different individuals, but even this is scarcely suffi- 

 cient to explain the wide discrepancies reported by vari- 

 ous investigators. Various authors 1 have reported the 

 presence of live and motile spermatozoa in the uterus of 

 dogs eight days after coition. Marshall and Jolly 2 found 

 live sperm-cells in the vasa deferentia of the rabbit ten 

 days after the removal of the testes, but all were dead at 

 thirteen days. The sperm-cells of bats are reported by 

 Benecke and others to be deposited in the female organs 

 in the autumn, there to remain dormant until the follow- 

 ing spring. Ovulation is induced by the warm weather 

 of early spring and the spermatozoa which have lain 

 dormant throughout the hibernating period become active 

 and insemination occurs. In the domestic hen, accord- 

 ing to Lillie, 3 " The period of life of the spermatozoa 

 within the oviduct is considerable as proved by the fact 

 that hens may continue to lay fertile eggs for a period of 



1 Hertwig, "Handbuch der Entwicklungslehre." 



2 Marshall and Jolly, " The (Estrus Cycle in the Dog." Phil. 

 Transactions. B., vol. 198, 1905. 



3 Lillie, "The Development of the Chick," 1908, p. 35. 



