364 



University of California Puhlications. 



[Zoology 



the left. The cilia on the left side now beat strongly backwards. 

 The action of the membranellae and the curvature of the body 

 turn the animal so that it points in a new direction which is to- 

 ward the right and away from the buccal groove. The cilia on 

 the right side now beat backwards, and the animal proceeds in 

 the new direction. 



Zl 



Fig. 17.- — The various phases of the form of the body of the auimal while 

 executing a motor reaction. 



IV. MOTOR REACTION IN CUT PIECES. 



In order to further test the functions of the various parts of 

 the body in the motor reaction the animals were cut in several 

 pieces. The posterior tip of a large animal was removed (fig. 

 18). The piece A, on Aveak stimulus, gave a normal motor reac- 

 tion except that the posterior end did not bend to the left. The 

 body remained rigid and after moving backwards for a consid- 

 erable distance the animal turned toward the aboral side, that is, 

 toward the right as a result of the action of the membranellae as 

 seen in fig. 19. Fig. 19 shows that the point about which the 

 animal turns is not at the posterior end but near the middle of 

 the animal. 



