Ko. 647] FAMILY RESEMBLANCES 



of which have been so often the subject of debate and 

 argument. It is necessary to determine what resem- 

 blances or differences exist before causes can be explained. 

 This is a study of family resemblances in intellectual per- 

 formance, particularly in the field of science. 



By limiting the problem to the measurement of resem- 

 blances the advice of a gifted and successful worker in 

 this field is followed. He writes : 



It is impossible at present to estimate with security the relative 

 shares of original nature, due to sex, race, ancestry and accidental 

 variation, and of the environment, physical and social, in causing the 

 differences found in men. One can only learn the facts, interpret 

 them with as little bias as possible, and try to secure more facts.^ 



By this same limitation it is hoped that a serious and 

 common error will be entirely avoided, namely, the fail- 

 ure to realize the twofold nature of the problem of in- 

 heritance as ordinarily discussed. The following analy- 

 sis is so clear and the need of it so general that it is given 

 at length. 



Most sociological writers and some biologists are confused in their 

 use of the concept of heredity. When there is discussion of the rela- 



ity there is sometimes understood the original constitution of the 

 individual and sometimes his resemblance to parents and other rela- 

 tives. It is conceivable that the original constitution of son and 

 father might be exactly the same and yet the individual be so plastic 

 to environment that under different conditions there would be but 

 slight similarity between their performances. It is also conceivable 

 that there might be no similarity between the original constitution 

 of son and father, and yet the performance of each be determined by 



Under which of these extreme hypotheses would the current sociologist 

 call heredity strong or weak? The word heredity should be reserved 

 for resemblance due to a common germ plasm and some other word 

 found for the constitution of the fertilized ovum or zygote; perhaps 

 the best that can be done is to use this uncouth word. We can then 



blance between the zygotes of two brotliers ? How far does the zygote 

 of an individual determine his performance as an adult? - 



iThorndike, "Educational Psyoholoffv," Vol. III. p. 310. 



2 J. McKeen a-ittell, "Families of Aim>ricari ^len of Scionce," Pop. Sci- 



