i8o MENDELISM ' chap 



at present very little definite evidence for supposing tha 

 what appear to be special forms of ability may be due t< 

 specific factors. Hurst, indeed, has brought forwarc 

 .some facts which suggest that musical sense sometimes be 

 haves as a recessive character, and it is likely that th( 

 study of some clean-cut faculty such as the mathematica 

 one would yield interesting results. 



The analysis of mental characters will no doubt b( 

 very difficult, and possibly the best line of attack is t( 

 search for cases where they are associated with som( 

 physical feature such as pigmentation. If an associatioi 

 of this kind be found, and the pigmentation factors b( 

 determined, it is. evident that we should thereby obtaii 

 an insight into the nature of the units upon which menta 

 conditions depend. Nor must it be forgotten that men 

 tal qualities, such as quickness, generosity, instability 

 etc., — qualities which we are accustomed to regard a: 

 convenient units in classifying the different minds witl 

 which we are daily brought into contact, — are nol 

 necessarily qualities that correspond to heritable units 

 Effective mental ability is largely a matter of tempera 

 ment, and this in turn is quite possibly dependent upor 

 the various secretions produced by the different tissue: 

 of the body. Similar nervous systems associated wit! 

 different livers might conceivably result in individuals 

 upon whose mental ability the world would pass a verj 

 different judgment. Indeed, it is not at all impossibl( 



