PREFACE XV 



delism/ it may be said that Darwin's law of selection as a 

 natural explanation of the origin of all fitness in form and func- 

 tion has also lost its prestige at the present time, and all of 

 Darwinism which now meets with universal acceptance is the 

 law of the survival of the fittest, a limited application of Darwin's 

 great idea as expressed by Herbert Spencer. Few biologists 

 to-day question the simple principle that the fittest tend to 

 survive, that the unfit tend to be eliminated, and that the 

 present aspect of the entire living world is due to this great 

 pruning-knife which is constantly sparing those which are best 

 fitted or adapted to any conditions of environment and cutting 

 out those which are less adaptive. But as Cope pointed out, 

 the survival of fitness and the origin of fitness are two very 

 different phenomena. 



If the naturalists have failed to make progress in the search 

 for causes, I believe it is chiefly because they have attempted 

 to reason backward from highly complex plant and animal 

 forms to causes. The cart has always been placed before the 

 horse; or, to express it in another way, thought has turned 

 from the forms of living matter toward a problem which involves 

 the phenomena of living energy ; or, still more briefly, we have 

 been thinking from matter backward into energy rather than 

 from energy forward into matter and form. 



All speculation on the origin of life, fruitless as it may at 

 first appear, has the advantage that it compels a sudden re- 

 versal of the naturalist's point of view, for we are forced to 

 work from energy upward into form, because, at the begin- 

 ning, form is nothing, energy is everything. Energy appears 

 to be the chief end of life — the first efforts of life work toward 

 the capture of energy, the storage of energy, the release of 



' Mendelism chiefly refers to the distinction and laws of distribution of separable or 

 unit characters in the germ and in the individual in course of its development. 



