MOVEMENTS OF THE EARTHWORM 



623 



that is moving in a straight line is made to assume a new course 

 by turning the sector to the left (see fig. 2, b), it can still be re- 

 directed in an opposite way by quickly turning the sector to the 

 right (see fig. 2, c). If, before the worm has passed beyond the 

 limits of the sector, the sector is once more turned to the left, 

 a third reaction sometimes occurs at the head, which swerves back 

 to the right. The last reaction, according to the rule given above, 

 is generally weak, but that it is effective is shown by the fact that 

 the worm changes its course again. As a result of these manipu- 

 lations the worm creeps in a zigzag fashion, as shown in fig. 2, d, 

 and seemingly without any orientation. Careful observation, 



Fig. 2 



however, reveals the fact that the worm persisting in the direction 

 of the arrow, finally brings its body into a line coinciding with the 

 course of its movements. 



Returning now to the first problem set forth at the beginning 

 of this paper — Does the worm in locomotion function as a unit 

 or as an aggregate of independent components? — we may attempt 

 to answer it on the basis of the facts just stated. Friedlander, 

 defending his thesis that in locomotion the earthworm reacts as 

 a succession of independent segments, was obliged to attribute 

 reactions which obviously involve the entire organism to excep- 

 tional means of stimulation, thus restricting his analysis to normal 

 quiet creeping alone. But the experiments on the spontaneous 

 orientation of the worm show conclusively that also in quiet 

 creeping the worm reacts not as a chain of segments but rather as 



