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The responses of the starfish to light # have been divided 

 by Plessner (1913) into two categories those (both positive and nega- 

 tive) in which the eye spot aots as the receptor and those in which 

 the receptors are distributed over the surface and connected with der- 

 mal nerve net. Inasmuch as it is the whole surface which possesses 

 these receptors and not merely that at the tip of the ray, it would b 

 well here to look into the qualities of the orientation of the tube 

 feet and their coordination that can be brought about through stim- 

 ulating the body wall. 



In starfish which are suspended and the body wall at one 

 side of a ray stimulated by gentle contact I have observed that th 

 tube feet in that region show a tendency to orient themselves in the 

 direction of the stimulus. Upon increasing the strength of the stim- 

 ulation of the body wall, the tube feet near the stimulated area under- 

 go retraction which spreads in proportion to the strngth of the stim- 

 ulus. I have s^en no orientation of the tube feet directly away from 

 the stimulus even though the stimulus be graded in intensity as care- 

 fully as possible. The response is either orientation toward th 

 stimulus or retraction. 



In the above experiment we have an explanation of a positive 

 response to a dermal stimulation* A negative response can be regarded 

 on the above hypothesis as a positive reaction toward the unstimulatad 

 side, if it should indeed prove to be a fact as indicated above that a 

 direct response to dermal stimulation is only positive in its sense. 

 Thus we may suppose that the tube feet are oriented toward the side 

 which receives optimal illumination, rather than that they are oriented 



# The older observers on the responses of starfish to light have 

 divided themselves into two schools* One of these schools regarded. the 

 eye spot as a light receptor and in it may be listed Romanes and Sw$rt 

 (1181), Oraber (1885), Preyer (1886), Bonn (1908). The rnorphologists 

 favored this view also. The second school regarded the light receptors 



