98 HEREDITY 



small, there is no evidence, or even likelihood, that 

 the gametes of a man or woman of, say, thirty-five 

 are in any way inferior to those produced ten years 

 earlier. If increasing years did indeed affect the 

 germ-plasm, either adversely or favourably, or in the 

 direction of greater or less variation, or, indeed, in 

 any fashion at all, the fact would obviously be of 

 immense importance to the student of heredity. 

 But if we confine ourselves to the normal reproduc- 

 tive period, there is no reason to believe that there is 

 any such relation between the age of the individual 

 and the nature of the germ-plasm. So far as his 

 knowledge of heredity can guide him, the observer 

 need have no cause to regret the present increase in 

 the average age at marriage — an increase which may 

 otherwise be welcomed for many reasons. But it is 

 well to recognise that there may be facts of import- 

 ance with which we are yet unacquainted as to the 

 influence of the age of the individual upon the germ- 

 plasm. So far we are able to make any definite 

 assertion only as to the relation between size of 

 family (which is obviously correlated with the age of 

 the parents) and mental characters. Thus Havelock 

 Ellis ^ finds that genius is one of the abnormalities 

 associated with families of large size. This holds 

 good whatever century be taken for study. Galton 

 (" English Men of Science ") obtained a like result, 

 as have other students. Toulouse, Magri, Langdon 

 Down and Cassel are quoted by Havelock Ellis as 

 having shown that insanity, imbecility, hysteria, and 

 neurasthenia are more frequent in large than small 

 families. It would obviously be premature to attempt 



1 " A Study of British Genius," 1904, pp. 106 et seq. 



