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THE AMERICAN NATURALIST [Vol. XLIII 



and even some of his conclusions were faulty, but never- 

 theless the credit belongs to him for establishing a point 

 of departure from which further developments of first 

 importance have come. The demonstration of so funda- 

 mental a fact has had no inconsiderable influence in the 

 understanding and interpretation of sense perception 

 among plants. 



Although many observers at first contended against the 

 possibility of such a propagation of stimulus and denied 

 the accuracy of Darwin's results, yet the general correct- 

 ness of his statements has been established even though 

 differences in interpretation may have crept in. One 

 reason, no doubt, why it was difficult to admit and support 

 Darwin's conception and to corroborate his results, is 

 that the region capable of perceiving a stimulus is so 

 localized and the conduction to the responsive area is 

 over so short a distance. One may gather from his writ- 

 ings that he did not regard the response to stimuli in the 

 nature of a release of a regulatory mechanism, as it is 

 now so commonly understood: his point of view indeed 

 as to the nature of such tropic responses as being merely 

 a modified form of circumnutation was against such an 

 interpretation. His attitude was of course that of the 

 teleologist, for he was ever keen to uncover purpose in 

 the reaction of organisms. In his concluding remarks 

 and summaries, while he suggested the interpretation of 

 such responses along the line of consciousness he ex- 

 hibited a considerable reserve and went no farther than 

 indicating the appropriateness of a comparison of the 

 similarity to the responses in lower animals. He did 

 not enter largely into the somewhat fruitless field of the 

 philosophical discussion of the question. His reserve 

 possibly but reflects the greater caution of a past genera- 

 tion m interpreting protoplasmic response universally in 

 terms of what we know about the problem in higher ani- 

 mal forms, but be that as it may, one is inclined to the 

 opinion that it was Darwin's own reluctance to commit 

 himself too unreservedly which restrained him, for in 



