108 THE TREND OF THE RACE 
The inheritance of arithmetical ability has been studied by 
Cobb who applied the ‘‘Courtis Tests in Arithmetic Series A” 
to the parents and children in eight families of the faculty of the 
University of Illinois. The records were compared with norms 
obtained by testing 200 students of the same institution of much 
the same degree of maturity and social status. Cobb studied 
particularly the relation between the aptitude for addition, 
subtraction, multiplication, division and copying figures in both 
parents and children. One individual may be good in addition 
and poor in division, and the endeavor was made to find if the 
relative of that individual would show the same distribution of 
aptitudes. The results of the study yielded considerable indica- 
tion of alternative inheritance of the traits in question. The 
average correlation with the mid parent was .49, with the like 
parent .60, with the unlike parent .o1. The numbers of individ- 
uals dealt with were too small to yield results which would be 
convincing by themselves, but they serve to corroborate the 
general conclusions of other investigatiors. The studies of 
Starch on the resemblance in the performance of scholars from 
the same family yield further confirmatory evidence. 
Next to Galton’s Hereditary Genius perhaps the best known 
investigation of the inheritance of mental traits is the work of 
Woods on Mental and Moral Heredity in Royalty. Members of 
royal families offer some peculiar advantages for such a study 
since their genealogies are matters of record to a greater extent 
than those of ordinary people; as a class they are free from the 
struggle for livelihood and have usually enjoyed educational 
advantages of a superior kind. Differences in environment 
probably affect the intellectual development of royalty much less 
than that of the majority of mankind. 
The study of Woods embraced all members of the royal families 
of Europe about whom information could be secured. Individ- 
uals were grouped according to their intellectual ability into ten 
catagories, number 1 including those generally adjudged to be 
imbeciles, number 10 including only a few of the most illustrious 
names, while the great majority naturally fell into the intervening 
