580 IOWA DEPARTMENT OF AGRICULTURE. 



that the male exercises no influence on prolificacy. Others claim that the 

 male does exercise an influence that is far-reaching. Some go to the length 

 of saying that the influence thus exerted is as great as that exerted by the 

 female, but a majority of those who hold to the view that males do 

 exercise such an influence are ready to concede that this influence is less 

 than that exerted by females. 



In the present discussion the question will first be examined as to 

 whether the male does influence j)rolificacy in procreation; and, second, 

 what is the relative strength of the influence compared with that of the 

 female. Of course, a negative conclusion as to the question first discussed 

 would preclude the necessity for discussing that other question. 



With quadruped females capable of producing more than one at a birth, 

 and which produce one in some instances and two in others, the different 

 results are the outcome of some influence exerted on procreation in the 

 dam rather than the result of chance. It is evident that such influence 

 comes entirely from the dam or entirely from the sire or partly from 

 both, or it comes from one or more of the sources named, aided by 

 external conditions such as food and environment. The ewe capable of 

 bearing twins does not always produce twins. Why should there be such 

 variation? The sow capable of producing twelve pigs at a birth, as 

 Sihown by the fact of such production, in another instance will produce 

 but six pigs at a birth. Why should that be? 



That the female does exert an important influence on prolificacy is 

 universally conceded. Some ewes produce only one lamb at a birth, 

 while others produce two, though mated to the same ram for successive 

 years. It may be asked, then, does not this prove that the ram does not 

 influence prolificacy? I answer no. The most that it can prove is that 

 the ram does not exercise as much influence on prolificacy as the dam. 

 Such evidence is negative rather than positive, for the same ram mated 

 with other ewes will in some instances result in but one at a birth and in 

 other instances in twins, which at least makes it possible, in the absence 

 of evidence to the contrary, that the ram does exert an influence on 

 prolificacy. 



It has been noticed that when but one ram is used in a flock the propor- 

 tion of twins from the earlier births is greater than from those later. 

 From this it has been argued that this result follows from the greater 

 vigor possessed by the ram. But if vigor in the ram influences prolificacy 

 then, by parity of reasoning it does in the ewe, hence it is conceivable 

 the result stated may come partly or chiefly or even wholly from the 

 ewe, as the more vigorous among the ewes come first into heat. But it is 

 almost certain that some of the influence resulting in plural births comes 

 from the ram, as, if the said ram, enfeebled by excess of service, was then 

 turned in to mate with the ewes of another flock, equal in prolificacy and 

 vigor to the former, it is almost certain that a less proportion of twins 

 would be produced in the earlier births. It is also true that Poland- 

 China sows enfeebled by injudicious management when mated with 

 Poland-China boars similarly enfeebled will produce fewer at a birth than 

 if mated with vigorous Tamworth sires. This at least is the result of 

 limited observation. If it could be sustained by facts the result of well 

 conducted experiments, it would settle the question, at least as to the 



