author's abstract op this paper issued 



BY the bibliographic SERVICE, APRIL 11 



THE LOCOMOTION OF THE HOLOTHURIAN 

 STICHOPUS PANIMENSIS CLARK^ 



G. H. PARKER 



ONE FIGURE 



Stichopus panimensis is a holothurian found in considerable 

 numbers on the rocky shores near the Scripps Institution for 

 Biological Research at La Jolla in southern California. Living 

 individuals under normal conditions measure about 25 centi- 

 meters in length. In relatively quiet waters they may be seen 

 creeping about in a manner that resembles superficially the 

 locomotion of a gigantic caterpillar, in that waves of movement 

 pass over them from end to end. 



Stichopus normally attaches itself to the substrate by its 

 trivium, whose three rows of ambulacral feet are essential to its 

 locomotion. Creeping is accomplished in part by a muscular 

 wave that originates at the posterior end of the animal and 

 sweeps over it to the anterior end. Before the locomotor wave 

 begins the whole length of the body of Stichopus is attached to 

 the substrate by its numerous ambulacral feet (fig. I, A). With 

 the first appearance of this wave, the feet of the posterior portion 

 are loosened from the substrate and the whole hind end is lifted 

 well above that surface. The posterior portion of the animal 

 then contracts vigorously on its length thus carrying the hind 

 end forward to a new position (B), in advance of that which it 

 formerly occupied. 



In this new position the posterior portion is then reapplied 

 to the substrate, to which its ambulacral feet again become 

 attached while the wave moves on to the middle of the animal 

 (C). As this portion is becoming attached, the wave reaches 

 the head, which is now projected forward (D) and finally attached 

 to the substrate, when the condition characteristic of rest is 



1 Contributions from the Zoological Laboratory of the Museum of Compara- 

 tive Zoology at Harvard College, No. 329. 



205 



