282 POPULAR SCIENCE MONTHLY 



Looking back upon our general summary of this modern formula- 

 tion of development as a whole we may ask what its value may be. 

 The chief importance lies in the fact that it permits one to bring the 

 generally accepted facts of racial and individual development under a 

 single phrase. Even though the words are used in a slightly different 

 sense, it is evident that chance gives the variations upon which all 

 development must be based, even though the factors that we must 

 assume to bring about the chance result are not altogether the same in 

 the racial as in the individual development. The process of selection 

 is also much the same throughout, for selection results from mere sur- 

 vival of one and rejection of others. 



The main lack in the formula is our inability at present to analyze 

 or define all the selecting agents. The environment in general which 

 serves as the agent in racial development is comparatively well under- 

 stood, or at least the meaning of the word and the methods of producing 

 results give definite pictures. On the other hand, the physico-chemical 

 constitution of the organism which must be assumed in the lowest 

 organisms, and the intimate nature of social pressure which is effective 

 in man both need much more complete analysis. And even pleasure 

 and pain are not as simple or as free from ambiguity as we are inclined 

 to suppose at first sight. But at least each of them marks a fairly 

 definite field for investigation and will serve in so far to satisfy the 

 needs of a formulation of the facts already known, and act as a spur 

 to further work. 



