DE VRIES'S THEORY OF MUTATIONS. 223 



learn to analyze the elements of the phenomenon, the probability grows 

 that sometime we shall master the art of actually directing the series 

 of natural phenomena. A new and limitless field of work would then 

 be opened. Provisionally we can guess only from what we have as 

 yet observed that certain processes are able to call forth or to accelerate 

 the phenomena of mutation. Thus de Vries suggests the idea that a 

 rapid succession of periods of reproduction might facilitate the reap- 

 pearance of a period of mutation, whilst others think that transporta- 

 tion into quite different surroundings or transplantation might produce 

 it. Others, again, appear to believe that increased nutrition, either 

 combined with the conditions mentioned or not, would call forth muta- 

 tion. All this, however, is no more than guesswork and hypothesis. 

 We have as yet no means of fully knowing and of understanding. 



For the present it is safer to recognize our absolute ignorance, and 

 at the same time to define more exactly how far de Vries has brought 

 us, and what is the important step for which we have to thank him. 

 We can warmly recommend the reading and studying of de Vries 's 

 clearly written and beautiful book. He has been the first to show us 

 the sharp distinction that exists between chance variation and fluc- 

 tuating variation, and to prove that it is not the latter, but the former, 

 that calls forth in nature the origin of species. He has not yet been 

 able to tell us whether, and, if so, how, chance variation could be called 

 forth artificially by man. The fact that artificial selection of fluc- 

 tuating varieties, as well as hybridizing, etc., has already led to such 

 indisputable improvements in the different races of animals and 

 plants may, however, give us hope that a conscientious experimenter 

 and close observer, such as de Vries, has still a full store of important 

 pioneer's work before him and may yet succeed in finding how to 

 direct the mutation process. Thus, the origin of species would not 

 only have been studied more closely, but would be subjugated to the 

 human will. After having seen species originate in nature, man 

 would then be able to call them forth. Then only the 'Origin of 

 Species,' to which Darwin has given us such a marvelous introduction, 

 would be revealed in all its details. 



IT-Jiv*. 



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