206 G. H. PARKER 



resumed (E). The effect of the locomotor wave as it passes off 

 at the anterior end of the animal is to carry this end as far for- 

 ward as the posterior end was advanced, and in this way Stichopus 

 moves forward step by step over the substrate. 



Animals about 25 centimeters in length were found to creep a 

 meter in about 15 minutes. When they were watched closely, 

 they were found to draw the tail forward and project the head 

 about 7 centimeters for each locomotor wave and these waves 

 occurred about once a minute. Never more than one wave at 

 a time was observed on the body of Stichopus. Usually a few 



cT 



B 



C 



Fig. 1 Diagrammatic figures of the passage of a single locomotor wave over 

 the body of a Stichopus panimensis. ^4, resting position; B, initiation of wave at 

 posterior end; C, wave at middle of body, posterior end returned to substrate; 

 D, wave passing off at anterior end; E, new resting position. 



seconds intervene between the time at which a given locomotor 

 wave disappears from the anterior end and a new one appears 

 at the posterior end. 



In an individual whose resting length was between 24 and 25 

 centimeters and whose creeping was watched for some time, the 

 locomotor waves passed over its body in intervals that varied 

 between 52 and 70 seconds with an average of 63 seconds. Conse- 

 quently the rate of these waves must have been about 0.39 

 centimeters per second, or approxmiately one-sixth to one- 

 seventh as rapid as that of the neuromuscular wave of a creeping 

 earthworm. 



