StatiHtinil In rcufigntions 

 Isoffciut or [j'mes of Kiiiud Ferlility. 



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nitistrations of the accuracy of the Isogeris. 



Piohiihly ;i little .'Kljustmeiit would give a better fitting plane to the 

 portion of the surtace under consideration, but Galton's rule gives at .my 

 rate a first approximation of a quite serviceable kind. 



Our author notes the curious chimge in the direction of the isogens svhen 

 the wife is older than the husband. Tliis seems to me to indicate that when 

 the wife is older than the husband, the age of the latter is of minor import- 

 ance. Galton interprets it as follows: 



"When she [the wife] is from thirty to thirty -eight she certainly .seems to h*'. appreciably 

 more fertile with a husband of her own age or somewhat older than she is [than] with one who 

 is younger'. I should hesitate to ascribe this to physiological causes without corroborative 



' The following results drawn from his data do not soem to confirm Galton's views : 



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