MENTAL CHARACTERS IN MAN 147 



the same time, he finds it impossible to define, except 

 in the roughest way, the innate bases of these heredi- 

 tary pecuharities. He concludes that we are com- 

 pelled to believe the}' consist in " inherited mental 

 structures of very considerable degrees of specialisa- 

 tion." McDougall points out that biologists and 

 statisticians, in studying the inheritance of mental 

 qualities, have frequently used crude and non- 

 psychological popular distinctions, such as good 

 temper, courage, conscientiousness, or popularity, 

 and emphasises the need for accurate psychological 

 anal3'sis of the constitution of the mind as a basis for 

 the study of mental inheritance. Biologists must 

 undoubtedly look to psychologists for aid in this 

 direction. In speaking of ps3'chic characters we are 

 not merely referring to the grosser mental differences, 

 such as feeblemindedness and the presence or absence 

 of musical, mathematical, or general ability, whose 

 inheritance is almost universallv admitted ; but to 

 the less readil}' definable traits which go to make up 

 what we call temperament, disposition, and character. 

 These have not yet received adequate biological 

 classification, treating them as methods of reaction ; 

 but such a scheme, combined with observations and 

 comparison of the elements of human characters, 

 would certainly help to clarify our conceptions con- 

 cerning the basis of the differences involved. 



May it not be also that in individuals who are 

 heterozygous for various character traits which are 

 alternative in inheritance, either method may come 

 into expression according to circumstances ? And 

 since every individual may be supposed to be hetero- 

 zygous for many pairs of traits of human character, 

 it appears possible that mental traits generally difiVr 

 from structural characters in that , in the former, all the 

 alternative possibilities may come into expression in 

 the same individual at different times, thus adding to 



