RELATION OF RACE CROSSING TO THE SEX RATIO. 203 



mental factors such as climate are concerned there can be no dif- 

 ferential effect on the sex-ratio for the two groups since all the 

 statistics are derived from the population of a single city. In a 

 general sense all the individuals live in the same environment. 

 But there is a possibility of a difference between the different 

 groups in regard to the complex of environmental factors which 

 are collectively implied in " social status." It is conceivable that 

 on the average the Italian -Argentine families are of different social 

 status than Italian-Italian or Argentine-Argentine families in the 

 same city. Differences in social status imply differences in nutri- 

 tion, in housing and in other physical conditions of existence. 

 Some one or all of these things might conceivably be held to 

 affect the sex-ratio in the manner observed. In considering this 

 point it needs to be held clearly in mind that there are two dis- 

 tinct questions involved. These are : {a) Is there any conclusive 

 evidence that there does exist as a matter of fact any uniform 

 average difference in the social status of individuals in cross as 

 compared with pure matings ? And {/?) granting that such an 

 average difference does exist what evidence is there that it would 

 produce the observed effect on the sex-ratio ? To the first of 

 these questions it is difficult to get any answer. Careful study 

 of all the available demographic statistics of Buenos Ayres has 

 failed to yield any conclusive evidence on the point. The prob- 

 ability appears to be, however, that if any difference at all exists 

 in the social status of the two groups it is in the long run (or on 

 the average) not marked in degree. Further it appears probable 

 that whatever difference does exist is in the direction of a lower 

 social status in the case of the cross matings. 



Regarding the influence of such a difference (if it exists) on the 

 sex-ratio it seems probable that it would have very little or no 

 effect. Punnett^ has recently made a very careful study of just 

 this point for certain elements of the population of London. He 

 finds that in the classes of lower social status more females than 

 males are born, and 7nce versa, but concludes in general that pa- 

 rental nutrition has no sensible influence on the sex-ratio. Mor- 

 gan^ reviews the literature on the subject and reaches the fol- 



' Punnett, R. C, "On Nutrition and Sex Determination in Man," Proc. Camb. 

 Phil. Soc, Vol. 12, 1903. 



2 Morgan, T. H., " Experimental Zoology," New York, 1907, pp. xii -(-454. 



