PEOGBESS IN ZOOLOGY — WILSON. 407 



allowance for the role of single '' lucky accidents " in evolution than 

 did many of the earlier evolutionists. And yet, as far as the essence 

 of the principle is concerned, I am bound to make confession of my 

 doubts whether any existing discussion of this problem aifords more 

 food for reflection, even to-day, than that contained in the sixth and 

 seventh chapters of the " Origin of Species " and elsewhere in the 

 works of Darwin. 



Undeniably there is a large measure of truth in the contention that 

 natural selection still belongs rather to the philosophy than to the 

 science of biology. In spite of many important experimental and 

 critical studies on the subject Darwin's conception still remains to-day 

 in the main what it was in his own time, a theory, a logical con- 

 struction, based, it is true, on a multitude of facts, yet still awaiting 

 adequate experimental test. Simple though the principle is, its 

 actual effect in nature is determined by conditions that are too intri- 

 cate and operate through periods too great to be duplicated in the 

 experimental laboratory. Hence it is that even after more than 50 

 years of Darwinism the time has not yet come for a true estimate of 

 Darwin's proposed solution of the great problem. 



But there is still another word to be said. Too often in the past 

 the facile formulas of natural selection have been made use of to 

 carry us lightly over the surface of unsuspected depths that would 

 richly have repaid serious exploration. In a healthy reaction from 

 this purblind course we have made it the mode to minimize Darwin's 

 theory, and no doubt a great service has been rendered to our study 

 of this problem by the critical and sceptical spirit of modern ex- 

 perimental science. But there is a homely German saying that im- 

 presses upon us the need of caution as we empty out the bath lest 

 we pour out the child too. This suggests that we should take heed 

 lest we underestimate the one really simple and intelligible explana- 

 tion of organic adaptations, inadequate though it now may seem, 

 that has thus far been placed in our hands. And in some minds — if I 

 include my own among them let it be set down to that indiscretion at 

 which I have hinted — the impression grows that our preoccupation 

 with the problem as it appears at short focus may in some measure 

 have dimmed our vision of larger outlines that must be viewed at 

 longer range ; that we may have emphasized minor difficulties at the 

 cost of a larger truth. To such minds it will seem that the principle 

 of natural selection, while it may not provide a master key to all the 

 riddles of evolution, still looms up as one of the great contributions 

 of modern science to our understanding of nature. 



I have taken but a passing glance at a vast and many sided sub- 

 ject. I have tried to suggest that the tide of speculation in our 

 science has far receded ; that experimental methods have taken their 

 rightful place of importance; that we have attained to a truer per- 



