110 University of California Publications in Zoology [ V OL. 18 



glass surface and the pinning down of the middle section, but the 

 wave of contraction, as in normal creeping, can be easily observed 

 (%. 1). 



ABC 



Fig. 1. This shows the method of pinning the anesthetized region of the 

 worm. Kegion A has just made an anterior creeping movement and region C 

 can be seen making a coordinated movement. On account of being pinned 

 through region B, the anterior part of C is forced to buckle. 



The reversal of the direction of these movements is also possible. 

 Stimulation of the anterior end will cause the posterior end to attempt 

 creeping posteriorly with the anterior piece acting in perfect 

 coordination. 



If, now, the nerve cord be severed in the middle region without dis- 

 turbing the muscular connections a great deal, the coordinated move- 

 ments of the two ends cease and become independent each of the 

 other. It is possible when a worm is pinned and the continuity of 

 nerve in the anesthetized area is broken, that the anterior and pos- 

 terior ends may each be making locomotor movements in opposite 

 directions, showing an independence of action even though joined by 

 a muscular connection. There can be, therefore, no doubt that the 

 nerve cord carries, for some distance, impulses which are responsible 

 for locomotor movements. By pinning the worm to the cork, the 

 matter of tension has been eliminated and by cutting the nerve, the 

 transmission through the nerve cord has been removed and coordinated 

 movements cease entirely. 



AVhen such a worm with transected nerve cord and anesthetized 

 middle section is released from its cork plate and allowed to creep 

 freely, it is found that the coordination of anterior and posterior parts 

 is perfect. In this case, however, there is an entirely different 

 explanation. The coordination of the posterior end can not be due to 

 any nerve impulses from the anterior end, but each forward move- 

 ment of the anterior section causes a pull on the posterior piece and 

 this starts a chain of reflexes at the anterior end of the posterior piece 

 which run the length of this part of the worm and give rise to the 

 muscular contractions which normally would give rise to locomotion. 



