268 A. S. PEARSE. 



sand. It accomplishes this in the same way that it burrows and 

 also to some extent by bending and straightening the body. A 

 series of experiments was carried out to ascertain how deep Thy- 

 one could be buried in the sand and yet burrow out. The method 

 was to place an individual in the bottom of a jar containing sea 

 water to a depth of 55 cm., which was the height of the jac It 

 was then covered with sand to the desired depth. Individuals 



A B 



Fig. 2. Diagrams representing the shape of cross-sections in the middle of the 

 body of Thyotie as it burrows into the sand. The form shown in A precedes that 

 shown in B. 



were able to come to the top of the sand when covered under 

 fifteen centimeters but none came up through twenty centimeters 

 although ten large individuals were tested. 



Clark ('99) found that Synapta burrowed with the tentacles and 

 that it always went into the sand " head first." Thyone differs from 

 it quite strikingly in the latter respect but this difference is perhaps 

 no more than would be expected from the structural unlikeness 

 between the two forms. 



V. Feeding. 

 After an individual has been undisturbed for some time it 

 often extends the anterior end of the body and the tentacles and 

 makes feeding movements (Fig. i, A). In this extension the 

 longitudinal muscles pull the lantern forward and the circular 

 body muscles contract. The anterior end of the body is thus 

 everted, like the turning inside out of the finger of a glove. The 

 branched tentacles are then pushed out by the pressure of the 

 fluids within them and the action of the muscles in their walls. 



