266 A. S. PEARSE. 



attachment. A constriction might appear at either end as a ring 

 around the body and pass to the opposite end. These rings 

 usually moved over the body singly and a new one appeared 

 about every three minutes on an active individual. Sometimes 

 constrictions appeared simultaneously at both ends and neutralized 

 each other as they met in the middle. As one of these con- 

 stricted rings moved along the tube-feet were pulled from their 

 attachments and folded into it, and when they were again extended 

 they became fastened at points farther along in the direction of 

 locomotion. As has been stated, Tliyone apparently experienced 

 some difficulty in getting the tube-feet to detach themselves at 

 the proper time and this " ring-of-constriction " method was en- 

 tirely effective in simultaneously pulling them loose in a certain 

 region of the body. It is not intended to intimate however that 

 the tube-feet could not be detached and moved forward without 

 the use of these periodic constrictions. 



Perhaps the most striking feature of the locomotion on a solid 

 surface was the fact that it was without definite orientation. 

 Individuals moved with the posterior end in advance as often as 

 with the anterior end, and although the long axis of the body 

 was as a rule approximately parallel with the direction of loco- 

 motion, animals often moved a long distance (as much as 12 cm.) 

 with the body at right angles to the direction of movement, that 

 is, they moved straight toward the right or left. The rate of 

 locomotion was slow, the most rapid movement recorded being 

 seven centimeters in fifteen minutes, or nearly half a centimeter 

 per minute. In climbing up a vertical surface like the side of a 

 dish the movements were not essentially different from those 

 which took place when an individual was creeping on a horizontal 

 surface. 



2. Burrowing. — When Thyotie is placed in a dish of sea water 

 on a sandy bottom it usually twists and turns the body until it 

 comes in contact with the side of the vessel. It attaches itself to 

 the side, burrows downward, and then moves away from the side 

 of the dish into the sand. The tube-feet are apparently of little 

 use in locomotion on sand, and this fact supports the conclusion 

 reached from watching their action on a solid surface, that they 

 are effective in pulling the body along rather than in pushing 



