PROGRESS IN ZOOLOGY — WILSON. 401 



whatever of its final validity. We do not adopt the mechanistic 

 view of organic nature as a dogma but only as a practical program of 

 work, neither more nor less. We know full well that our present 

 mechanistic conceptions of animals and plants have not yet made 

 any approach to a complete solution of the problems of life, whether 

 past or present. This should encourage us to fresh eli'orts, for 

 just in the present inadequacy of these conceptions lies the assurance 

 of our future progress. But the way of unverifiable (and irre- 

 futable) imaginative constructions is not our way. We must hold 

 fast to the method by which all the great advances in our knowledge 

 of nature have been achieved. We shall make lasting progress only 

 by plodding along the old, hard-beaten trail blazed by our scientific 

 fathers — the way of observation, comparison, experiment, analysis, 

 synthesis, prediction, verification. If this seems a prosaic program 

 we may learn otherwise from great discoverers in every field of 

 science who have demonstrated how free is the play that it gives to 

 the constructive imagination and even to the faculty of artistic 

 creation. 



Thus far I have desired to emphasize especially the reawakening of 

 our interest in problems of the present, and the growing importance 

 of experimental methods in our science. It is interesting to observe 

 how these changes have affected our attitude toward the historical 

 problem as displayed in the modern study of genetics. Even here 

 we are struck by the same shifting of the center of gravity that has 

 been remarked in other fields of inquiry. In the Darwinian era 

 studies on variation and heredity seemed significant mainly as a 

 means of approach to the problems of evolution. The post-Darwin- 

 ians awoke once more to the profound interest that lies in the genetic 

 composition and capacities of living things as they now are. They 

 turned aside from general theories of evolution and their deductive 

 application to special problems of descent in order to take up ob- 

 jective experiments on variation and heredity for their own sake. 

 This was not due to any doubts concerning the reality of evolution 

 or to any lack of interest in its problems. It was a policy of masterly 

 inactivity deliberately adopted ; for further discussion concerning the 

 causes of evolution had clearly become futile until a more adequate 

 and critical view of existing genetic phenomena had been gained. 

 Investigators in genetics here followed precisely the same impulse 

 that had actuated the embryologists ; and they, too, reaped a rich 

 harvest of new discoveries. Foremost among them stands the redis- 

 covery of Mendel's long-forgotten law of heredity — a biological 

 achievement of the first rank which in the year 1900 suddenly illumi- 

 nated the obscurity in which students of heredity had been groping. 

 Another towering landmark of progress is De Vries's great work on 

 18618°— SM 1915— —26 



