90 American Statistical Association. 



parents, and it is possible that at some future time, should 

 circumstances favor the undertaking, the data now on hand 

 may be utilized in this way. 



The curves showing the rate of growth of the above-men- 

 tioned selected American boys have been introduced into 

 Plate VI for comparison with the curves corresponding to 

 the observations on children of American and of Irish parent- 

 age. It is evident that the superior size of these boys, in 

 comparison with the average boys of American parentage 

 attending the public schools, cannot be attributed exclusively 

 to either of the factors which have been recognized as influ- 

 encing the dimensions of growing children ; for in the first 

 place the comfort in which the pupils of these selected 

 schools live and grow up must be greater than that enjoyed 

 by the generality of children of American parentage attend- 

 ing the public schools ; and in the second place, their ances- 

 tors for several generations are probably, in the majority of 

 cases, American ; while the children with whom they are 

 compared, though of American parentage, doubtless have, in 

 a great many instances, foreign grand-parents. Hence, what- 

 ever tendency residence in America may have to increase 

 the size of growing children will, in their cases, be intensified 

 by transmission through several generations. 



The characteristics which distinguish the various races of 

 men result from slow modifications of a common ancestral 

 type by the action through successive generations of the 

 varying conditions under which growth and development 

 take place. It is therefore interesting to inquire how quickly 

 the type of a race may be altered by a change in the external 

 conditions of development. We have already seen that, as 

 far as the height of the adult individual is concerned, a single 

 generation is, according to Dr. Gould, sufficient to produce a 

 marked effect. A most striking proof of this statement is 

 afforded by the tables given by this writer,* showing that 

 natives of New England and New York enlisting in the 



* Op. cit., pp. 126, 127. 



