38o THE POPULAR SCIENCE MONTHLY 



indicates that they are not purposeful, but we can not prove this. If 

 they are not purposeful then the purposefulness of the living world has 

 no direct relation to the origin of useful variations. The origin of an 

 adaptive structure and the purpose it comes to fulfill are only chance 

 combinations. Purposefulness is a very human conception for useful- 

 ness. It is usefulness looked at backwards. Hard as it is to imagine, 

 inconceivably hard it may appear to many, that there is no direct rela- 

 tion between the origin of useful variations and the ends they come to 

 serve, yet the modern zoologist takes his stand as a man of science on 

 this ground. He may admit in secret to his father confessor, the 

 metaphysician, that his poor intellect staggers under such a supposi- 

 tion, but he bravely carries forward his work of investigation along 

 the only lines that he has found fruitful. 



In the last analysis it is a matter of expediency; or if the word 

 jars, a matter of instinct. Wliy forsake the gold mine at our feet, 

 because the transmutation of metals is a philosophic possibility ? 



Whether definite variations are by chance useful, or whether they 

 are purposeful are the contrasting views of modern speculation. The 

 philosophic zoologist of to-day has made his choice. He has chosen 

 undirected variations as furnishing the materials for natural selection. 

 It gives him a working hypothesis that calls in no unknown agencies; 

 it accords with what he observes in nature; it promises the largest 

 rewards. He does not deny, if he is cautious, the possibility that there 

 may be a purposefulness in the sense that organisms may respond 

 adaptively at times to external conditions; for the very basis of his 

 theory rests on the assumption that such variations do occur. But he is 

 inclined to question the assumption that adaptive variations arise he- 

 cause of their adaptiveness. In his experience he finds little evidence 

 for this belief, and he finds much that is opposed to it. He can foresee 

 that to admit it for that all important group of facts, where adjustments 

 arise through the adaptation of individuals to each other — of host to 

 parasite, of hunter to hunted — will land him in a mire of unverifiable 

 speculation. He fears to enter thereby on a field of exploitation of 

 nature that has proved itself so sterile in the past. 



We have reached the end of our theme. If I have led you too far 

 into some of the remote corners of zoological thought, I must plead 

 that such thoughts are the legitimate outgrowth of Darwinism. 



I have tried to show you the modern zoologist at work on the great 

 theory of evolution. We stand to-day on the foundations laid fifty 

 years ago. Darwin's method is our method, the way he pointed out we 

 follow, not as the advocates of a dogma, not as the disciples of any 

 particular creed, but the avowed adherents of a method of investigation 

 whose inauguration we owe chiefly to Charles Darwin. For it is this 

 spirit of Darwinism, not its formula, that we proclaim as our best 

 heritage. 



