Page:Popular Science Monthly Volume 68.djvu/286

 282 Looking back upon our general summary of this modern formulation 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 survival 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 understood, 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.