RELATION OF RACE CROSSING TO THE SEX RATIO. 205 



require confirmation from other sources and expeyiviental analy- 

 sis. Within their hmits, they lead to a definite and significant 

 conclusion as to fact. In so far they contribute to the discussion 

 of the general problem of determination of sex. 



Summary. 

 Statistics of over 200,000 human births extending over a pe- 

 riod of 10 years in the city of Buenos Ay res show that the pro- 

 portion of males to females is significantly greater when the 

 parents are of different racial stocks than when they are of the 

 same. In the data are involved three racial stocks in pure and 

 cross matings. The preponderance of males in the offspring of 

 cross matings appears not to be capable of explanation as the 

 result of environmental or demographic influences. Experimen- 

 tal investigations are necessary in order to reach adequate 

 explanations of such statistical facts regarding sex ratios as are 

 set forth in this paper. 



Biological Laboratory, 



Maine Experiment Station, Orono, Maine. 



