196 RAYMOND PEARL AND MAUD DEWITT PEARL. 



mate or illegitimate, and (c) what was the nationality of each of 

 its parents. Furthermore it should be said of these statistics that 

 they are registration figures and not census returns. That is to 

 say, they are definite records of events, each event being recorded 

 when it happens, not more or less inaccurate counts made a long 

 time after the event. Of the substantial accuracy of these figures 

 there can be no doubt. 



As is well known, Buenos Ayres is a city having a population 

 which is racially very heterogeneous. For a decade and more 

 past there has been a large Italian immigration. Also there has 

 been extensive Spanish immigration. Representatives from other 

 nations have come in in smaller numbers. From the statistics of 

 birth above alluded to it is possible to determine what has been 

 the sex of the offspring of each of these racial groups in pure 

 matings and when crossed with native Argentine stocks. For 

 the purpose of the present study the birth statistics of the ten 

 years 1 896-1 905 inclusive have been used. The following 

 matings have been considered : 



Data are available for other matings but it has not seemed advis- 

 able to deal with any yielding less than 8,000 offspring in the ten 

 years. The inquiry has been further limited to legitimate births, 

 because of the uncertainty which must always exist in the great 

 majority of illegitimate births as to whether the putative father is 

 the actual one. With these restrictions the number of separate 

 offspring dealt with in this study approaches a quarter of a million 

 (exactly 219,5 16). 



These statistics have been studied with the purpose of obtain- 

 ing answers to the following questions : 



I. Is there a tendency towards an excessive production of off- 

 spring of one sex (either male or female) in cross as compared 

 with pure matings, among the human racial stocks under con- 

 sideration ? 



