112 THE TREND OF THE RACE 



mindedness of various grades is recessive or partly recessive to 

 normal mentality, and if the lower grades of feeble-mindedness 

 tend to be recessive to the higher forms, we should expect to find 

 average ability recessive to superior ability. It is not an easy 

 matter, especially when dealing with incomplete records and with 

 characters which (like musical and artistic ability) are strongly 

 influenced by family traditions, to determine whether a given 

 character is dominant or recessive. The test of recessiveness is 

 given if the matings of parents both of whom have the character 

 in question produce children all of whom inherit this character. 

 But this test is never completely satisfied, although non-conform- 

 ing cases might conceivably be explained. 



We should get much the same results if the character were 

 dominant and several determiners were concerned in its produc- 

 tion as in the case of the dark color of various kinds of wheat and 

 oats. On the whole, I believe the inheritance of exceptional 

 ability is best explained — though I cannot here give in detail the 

 evidence for this conclusion — on the assumption that it depends 

 upon many factors which behave as dominants to those which 

 give rise to ability of an inferior kind. The fact that parents of 

 superior ability produce, though only occasionally, offspring 

 which, although normal and healthy, never come near to measur- 

 ing up to the intellectual capacity of their parents, is quite in 

 accord with this view, while opposed to the theory of the recessive 

 nature of superior mental endowments. Results of negro-white 

 crosses yield confirmatory evidence of the same view. 



Perhaps the doctrine that genius or great ability is a sort of 

 anomaly dependent upon some defect of the germ plasm has been 

 fostered by the rather prevalent notion that genius tends to be 

 associated with insanity. The doctrine expressed by Dryden in 

 the lines; 



"Great wits are sure to madness near allied, 

 And thin partitions do their bounds divide, " 



not only expressed a popular conviction, but the sober conclusion 

 of many scientific men who have devoted especial attention to the 



