LIFE AND MIND 



tiveness and contractility, responds to a greater 

 variety of more special external stimuli. Yet 

 the polyp, possessing no specialized organs of 

 sense, can oppose but one sort of action to 

 many diverse kinds of impression. Phenomena 

 so different as those of light and heat, sound 

 and mechanical impact, can affect it in but one 

 or two ways, — by causing it to move, or by 

 slightly altering its chemical condition. The 

 modes of response to outer relations are few 

 and homogeneous. Passing abruptly to civi- 

 lized man, at the other end of the animal scale, 

 we find a different state of things. To each 

 kind of external stimulus there are many pos- 

 sible modes of response. Not only, for exam- 

 ple, does the human organism sharply distin- 

 guish between variations which affect the eye 

 and those which affect the ear ; not, only do eye 

 and ear, which are themselves organs of amaz- 

 ing complexity, discern an endless number of 

 differing tones and hues, as well as a great 

 variety of intensities and qualities; but each 

 particular manifestation of sound or of light is 

 capable of arousing in the organism very differ- 

 ent psychical combinations, entailing different 

 muscular actions, according to circumstances. 

 Tennyson's traveller, who, walking at nightfall 

 in a strange land, hears the moaning of a dis- 

 tant sea, — 



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