RELATION OF RACE CROSSING TO THE SEX RATIO. 20I 



first instance with the statistics for three years (1903, 1904 and 

 1905) only. The figures for these years led to exactly the re- 

 sults which have been shown above. The figures for the seven 

 previous years were then taken into the calculation to see whether 

 they would confirm or reverse these results. That they confirm 

 them is clear. 



2. That the inclusion of living births only in the statistics in- 

 fluences the result. That statistics of sex should theoretically 

 include still-born as well as those born living is obvious. The 

 still-born would have been included in the tables of this paper 

 had it not been for the fact that the original material was tabu- 

 lated in such way as to render it impossible to include them. A 

 little consideration shows, however, that the absence of still-born 

 does not sensibly affect the conclusion drawn from the present 

 statistics. It is a well-known fact that among still-born children 

 the proportion of males to females is very much greater than 

 among living born. It does not seem necessary to cite evidence 

 of this fact ; all large collections of birth statistics show it. 

 Pains have been taken to make sure that the records of still- 

 born in Buenos Ayres form no exception to the general rule. 



Now there are three possibilities respecting the distribution of 

 still-born young among the offspring of the cross and pure 

 matings discussed in this paper. These are : 



(a) That still-births are distributed /to rata among cross and 

 pure matings. This is the most probable supposition. It would 

 be expected on general grounds that in the long run there would 

 be substantially the same number of still-births among a given 

 total number of births whether this total originated from cross 

 or pure matings. 



ib) That a relatively larger number of still-births originate 

 from pure than from cross matings. 



(c) That a relatively large number of still-births originate 

 from cross matings than from pure. 



It being a fact that still-births show a high sex-ratio it is evi- 

 dent that a distribution of such births in accordance with {b) 

 could alone tend to reverse the conclusion reached from statis- 

 tics which leave these births out of account. In case they were 

 distributed as in {a) or [c) their inclusion would simply make 



