49 POPULAR SCIENCE MONTHLY. 



of " sports," which, if useful, are seized upon and perpetuated by 

 selection. 



He says that a sport is a substantial change of type effected 

 by a number of small changes of typical center, each more or 

 less stable, and each being in its turn favored and established by 

 natural selection to the exclusion of its competitors. 



" The distinction between a mere variety and a sport is real 

 and fundamental." 



This generalization, based upon definite numerical data, is so 

 fundamental and far-reaching that a critical discussion of the 

 evidence is most important. 



IMITATION AMONG ATOMS AND ORGANISMS. 



BY EDMUND NOBLE. 



DURING the past dozen years scientific writers, American 

 as well as European, have given a certain amount of 

 attention to the part played in human life by imitation, with 

 especial reference to the conditions under which children acquire 

 from parents and associates the salient characters of individual 

 and social habit. But the examples drawn upon for illustration 

 have been narrow in their range, while the analogous process of 

 assimilation among the lower animals and in the realm of the 

 inorganic has received but scant recognition. It is proposed in 

 the present article to connect the three classes of phenomena by 

 formulating a general law which may serve, provisionally at any 

 rate, to cover them all, and then to group the phenomena in their 

 various natural divisions. 



Without taking note of its unimportant and obvious qualifica- 

 tions, the statement may be made that all things free to move, 

 capable of becoming closely associated, and impelled to move- 

 ment by the system to which they belong, tend to come together 

 when they are likes, and to be separated when they are unlikes. 

 If we regard this tendency from the point of view of the move- 

 ment, we shall say that likeness of things involves association of 

 them in the degree of their likeness, and that unlikeness of them 

 involves dissociation of them in the degree of their unlikeness ; 

 while, if we regard the tendency from the point of view of the 

 things themselves, we shall say that association of things in- 

 volves likeness of them in the degree of the association, while 

 dissociation of things involves or implies unlikeness of them in 

 the degree of the dissociation. These truths may be expressed in 

 a more general way by saying that in systems the association of 

 likes involves the least degree of resistance among them, while 



