BOTTOM MATERIAL INGESTED — HOLOTHURIANS 



383 



2. It is rather difficult to determine exactly the number of 

 times per day that these holothurians fill the intestine. Labora- 

 tory feeding experiments are quite useless, as the animals usually 

 will not eat when confined in vessels having vertical walls up 

 which they may creep. The castings do not retain, in the field, 

 a recognizable form for more than several hours, so that little 

 help can be had from that quarter. Moreover, these animals 

 move about to an extent which one would scarcely predict. 

 When viewed from the shore, they seem ponderously sluggish, — 



cms. 



Fig. 

 moebii. 



50 60 70 80 90 100 1(0 120 



Length of alimentary tract. 



2 Relation between length of animal and length of gut, in Stichopus 



a part of the bottom, — yet they do in fact exhibit quite decided 

 migratory movements, particularly in a vertical direction, in 

 appropriate places. Several attempts to get Stichopus to feed 

 upon a substratum prepared by mixing lamp-black with the 

 natural mud, in order that the mud might be recognizable if 

 swallowed, were unsuccessful. The examination of normal 

 intestinal contents plainly showed that the periods of emptying 

 were not characteristically coincident with tidal events. At- 

 tempts to discover the existence of any other form of regularity 



THE JOURNAL OF EXPERIMENTAL ZOOLOGY, VOL. 26, NO. 2 



