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THE AMERICA V NATURALIST 



[Vol. XLVI 



analytical and experimental work on the problem of the 

 factors of evolution was begun some twenty years ago 

 and has been continued with ever-increasing interest to 

 the present time. 



In the first enthusiasm over the experimental method 

 of attack it seemed to many students of this problem that 

 at last a path had been found which would lead straight 

 to the goal, that the causes of all evolution were about to 

 be revealed, and that the practical control of evolution, 

 with all that this implies, was almost within reach. About 

 that time a young physiologist said to the Director of 

 the Zoological Station at Naples, "Why do you spend so 

 much money publishing these beautiful monographs on 

 the Fauna and Flora of the Gulf of Naples ! " Dr. Dohrn 

 replied, "You are the first person who has ever asked me 

 such a question; many have asked how and where I got 

 the money, but no one has asked why. What do you 

 mean!" "Only this," said the physiologist, "that 

 within twenty-five years we shall be making experiment- 

 ally an indefinite number of faunas and floras, and the 

 present one will then be only one of many." In the 

 opinion of many investigators at that time, experimental 

 evolution was soon to give us a new world of living 

 things, and it was about to reveal conclusively the causes 

 of evolution. We have now had one or two decades of 

 this experimental evolution, and it may be worth while 

 to inquire, What has been the net result? If the answer 

 should seem to be somewhat discouraging I would beg to 

 remind you that is so chiefly because the problems have 

 been found to be much greater than was at first supposed. 

 The experimental method as applied to the evolution 

 problem has justified itself ; it has set the problem in a 

 clear light and it has brought forth facts of the greatest 

 significance, but it has not enabled man to do in twenty- 

 five years what it took nature twenty-five million years 

 to do. 



I 



The most significant work on genetics since the time 

 of Darwin is that which is identified with the name of 



