82 HEREDITY AND SOCIAL FITNESS 



strains. Should this occur for a number of generations, the point may 

 be reached where fair and good abihty would still appear in the off- 

 spring, even though there be outmating with very low ability; that 

 is, relative absence in the germ-plasm of the better consort would 

 behave as relative presence to the lack of determiners in the weaker 

 consort; the resulting simplex individual would show and be able to 

 transmit fair ability. The only serious danger would accrue from 

 matings in two or more consecutive generations with very low or no 

 ability, when there would be a reversal of the process, and the produc- 

 tion of an increasing number of children having low or no ability. 

 We have here, then, segregation, a real alternative inheritance; but 

 the segregation is that of units of progressively higher potency. 



The limits to the development of this trait would naturally be set 

 by the grade of the ability in the general population. Mating of a 

 high or medium with a low grade would insure the production of an 

 increasing number with high or medium ability and the final elimina- 

 tion of those having low or no ability. This process is amply illus- 

 trated in Lines A and C. 



A word may be added here regarding the origin of strains showing 

 unusual calculating ability. In rare instances, individuals have 

 shown this faculty in an abnormal state of development. The wTiter 

 has recently met a man whose business it is to calculate the invoices 

 for the large mercantile houses of his city. He is *able to invoice the 

 charges covering a period of 6 months in 40 hours, the totals involved 

 amounting to hundreds of thousands of dollars. For the purpose of 

 calculation he uses a piece of paper 2x3 inches. His accuracy, as 

 determined by actual test, is equal to that of a calculating machine 

 and his speed 20 per cent greater. Both of his parents were from strains 

 showing superior native ability in calculation. The distribution of 

 this ability in his fraternity is as follows : two members show very high 

 ability, three members medium, three members low ability, though 

 in this case the low ability is considerably in advance of the calculating 

 ability in the general population. Here, again, there has evidently 

 been segregation of two unit-like series of high potency, the two who 

 show the highest abihty having been produced by the double presence 

 of two highly potent series, one contributed by the maternal, the other 

 by the paternal germ-plasm. 



2. Aggressfv^eness. 



The application of the term aggressiveness has been given in the 

 opening sections, with a sufficient number of illustrations in the his- 

 tories that follow to make its meaning clear. 



In evaluating such a trait or trait-complex as aggressiveness we are 

 confronted by enormous difficulties. The social inheritance plays a 

 far larger part in its manifestation than it does in calculating abihty, 



