REPRODUCTION 49 



be bred not less than thirty hours after the beginning 

 of heat. In practice, the animal-breeder may safely 

 assume that the normal active existence of the sperm- 

 cells in the uterus of mammalian animals is' short and 

 that therefore to insure successful conception, the actual 

 service of the male should occur very near to the time 

 when the heat is at its height. 



48. Effect of intoxication of the male parent on his 

 offspring. The fertilized egg may be so influenced by 

 various environmental factors that the embryos arising 

 from such eggs are affected in a definite way. Similar 

 effects from factors calculated to influence the sperm- 

 cells are much more obscure. It is very difficult from 

 the very nature of the factors involved to influence the 

 sperm-cell in such a definite way that the influence will 

 directly modify the offspring. -Observations on this 

 point have been numerous but few experiments under 

 proper control have been made. In all experiments 

 conducted for the purpose of influencing the male germ- 

 cells, it is necessary to work through the animal body. 

 Under these circumstances it is not always easy to deter- 

 mine with certainty whether the modifications resulting 

 from various treatments are the direct result of the treat- 

 ment on the sperm-cell or the secondary effects from the 

 changes in the parental body itself. Among humans 

 it is generally recognized that indulgence in. alcoholic 

 drinks by the male results in various defects in the off- 

 spring. In one observation Lippich studied ninety-seven 

 children conceived during intoxication. Of this number 

 all were defective except fourteen. 1 Among seven births 



^tockard, "Effect of Intoxicating the Male Parent," Amer- 

 ican Naturalist, vol. 47, p. 641 ; also Journal of Heredity, vol. 

 5, Feb. 1914. 



