42 MAN [Chap. VIII 



Letter 411 much considered the subject of the causes of the propor- 

 tion. When I reflected on queen bees producing only males 

 when not impregnated, whilst some other parthenogenetic 

 insects produced, as far as known, only females, the subject 

 seemed to me hopelessly obscure. It is, however, pretty clear 

 that you have taken the one path for its solution. I wished 

 only to ascertain how far with various animals the males 

 exceeded the females, and I have given all the facts which I 

 could collect. As far as I know, no other data have been 

 published. The equality of the sexes with race-horses is 

 surprising. My remarks on mankind are quite superficial, 

 and given merely as some sort of standard for comparison 

 with the lower animals. M. Thury is the writer who makes 

 the sex depend on the period of impregnation. His pamphlet 1 

 was sent me from Geneva. I can lend it you if you like. I 

 subsequently read an account of experiments which convinced 

 me that M. Thury was in error ; but I cannot remember what 

 they were, only the impression that I might safely banish 

 this view from my mind. Your remarks on the less ratio 

 of males in illegitimate births strikes me as the most doubtful 

 point in your MS. — requiring two assumptions, viz. that the 

 fathers in such cases are relatively too young, and that the 

 result is the same as when the father is relatively too old. 



My son George, who is a mathematician, and who read 

 your MS. with much interest, has suggested, as telling in the 

 right direction, but whether sufficient is another question, that 

 many more illegitimate children are murdered and concealed 

 shortly after birth, than in the case of legitimate children ; 

 and as many more males than females die during the first few 

 days of life, the census of illegitimate children practically 

 applies to an older age than with legitimate children, and 

 would thus slightly reduce the excess of males. This might 

 possibly be worth consideration. By a strange coincidence 

 a stranger writes to me this day, making the very same 

 suggestion. 



I am quite delighted to hear that my book interests you 

 enough to lead you to read it with some care. 



1 Mhnoire sur la lot de Production des Sexes, 2nd edit., 1863 (a 

 pamphlet published by Cherbuliez, Geneva). 



