272 



Mr Punnett, 

 Table IX. 



Total no. of children = 894, No. of families = 296. 



We may take it, therefore, that there are good grounds for 

 stating that in the first one or two births in a family there tends 

 to be a preponderance of ,/s, whilst in later births the % s are as 

 numerous as the Js, even when the total number of <?s is con- 

 siderably greater than that of the ? s. Consequently the larger 

 the size of the family the greater the relative number of $s. 

 And we are probably safe in expressing this otherwise as — the 

 higher the birth-rate the greater the relative preponderance of 

 $s. Now in our London groups the birth-rate in the poorest, 

 A, is nearly double that of the wealthiest, C (vide Table V) ; 

 whilst that of B is intermediate between the two. From this we 

 should be led to expect a comparative preponderance of % s in A 

 as compared with B, and again in B as compared with G. In 

 Table I it has already been seen that this is actually the case. 

 And it was there pointed out that such a result was not in accord 

 with other observations on the influence of nutrition on sex. In 

 the influence of the comparative birth-rate it would seem that we 

 have some explanation of the preponderance of $s among the 

 poorest nourished classes. The greater size of the family here 

 means a relative preponderance of $ s as compared with the better 

 nourished districts where for some cause or other the size of 

 the family is less, and the ^s consequently are in the majority. 



(4) Influence of the age of the parents. 



Though I have not been able to collect any convincing evidence 

 that the age of the father influences the determination of sex, the 

 following data from Queen Charlotte's Lying-in Hospital would 

 seem to shew that the age of the mother may have some effect. 

 This material (which is tabulated in Table X) consists of 6938 

 cases of primiparas in which the age of the mother, together with 



