26 STATISTICS OF SEX 



ninth child onward \ve find an excess of males which generally exceeds 

 the normal all through. But it is not at all certain that this arises 

 from a unisexual tendency in the case of older parents. It is quite 

 possible that it may he attributed to first-born children after remar- 

 riage, the table having been constructed without any reference to the 

 mother and giving only children in families by the same father. It 

 must also be noted that the total numbers beyond the tenth child be- 

 come too small to predicate a very certain conclusion upon. A more 

 complete investigation of the subject will therefore be necessary before 

 it can be said with certainty whether the results derived by Bosenthal in 

 the Vienna statistics in the case of old parents are correct, or whether 

 we here have to do with the first-born of second or third wives. 



It might appear, at first sight, that these statistics do not decide 

 whether the variation in the proportion of male and female, as the 

 family advances in number, are due to the male or female parent. But 

 a consideration of the ratio between the number of acts on the part of 

 the two parents who are concerned in the case, decides the probabilities 

 in favor of the mother. 



A more conclusive investigation than has as yet been made is neces- 

 sary to absolutely decide whether, as has been suggested in this paper, 

 the part of the father is completely asexual. To make this investiga- 

 tion, it is necessary to compare the statistics of births by mothers of one 

 and the same class with fathers of different ages. Since the ratio of 

 male to female is the same, at least from the third to the eighth birth, 

 the preferable method is to confine the investigations to those births 

 which may be grouped all together, so far as the mother is concerned. 

 We then compare the sex of each child of this class with the age of its 

 father and, by a sufficient accumulation of cases, ascertain whether 

 the ratio varies with that age. 



8. EXAMINATION OF CERTAIN OTHER CONDITIONS WHICH HAVE 

 BEEN SUPPOSED TO INFLUENCE THE PRODUCTION OF SEX. 



It has sometimes been supposed that the destruction of an important 

 fraction of the male population of a country by war, such as has occa- 

 sionally been known in history, has resulted in a greater preponderance 

 of male offspring in the country so affected. A very slight analysis of 

 the supposed cause will show that this proposition belongs to a class 

 which require very strong proof. Granting the truth of the proposi- 

 tion : since those who were killed in war could not subsequently have 



