124 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



crawl about or bury themselves. They do not bore their way 

 into the sand by means of the tentacles and anterior end of 

 the body, as is described below for Synapta, but lie with the 

 ventral side upon the surface of the sand, and, by alternately con- 

 tracting and extending their bodies, push the sand aside and 

 gradually sink beneath the surface. The pedicels of the ventral 

 side of the body aid in pushing aside the particles of sand and 

 drawing the body down. 



Cucumaria. — According to observations of Grave* at Beau- 

 fort, North Carolina, Cucumaria pulcherrima likewise lives in a 

 U-shaped tube near the surface of the mud near low-water 

 mark. The individuals of this species even when very young 

 show a remarkable sensitiveness to stimuli caused by vibrations, 

 and quickly withdraw the tentacles at the slightest disturbance. 

 Specimens reared from the free-swimming stage, however, and 

 kept in the laboratory for two or more years lose the irritability 

 characteristic of newly caught individuals, so that even when 

 removed from the aquarium with such force as to tear off many 

 of the tube-feet they may fail to draw in the tentacles. 



When feeding, they extend the branched tentacles to half the 

 length of the body and gather up the diatoms and other organic 

 matter from the surface of the mud, as described for Thyone. 

 In cold weather they cease feeding and remain for long periods 

 of time with the tentacles withdrawn. 



Synapta. — The common Synapta secures its food in the 

 same way as Thyone. 



In life the tentacles are almost constantly in action, reaching 

 out in all directions to explore surrounding objects, the digits, 

 or slender branches of the tentacles, being thrust out and curled 

 up incessantly. They secure the food and serve in burrowing. 

 In making the burrow, as described by Clark, f the animal bores 

 vertically down into the sand with the oral end foremost. The 

 tentacles are used to remove the particles of sand in front. 



" Synaptas burrow into the sand head first, and almost always 

 go straight downward for some distance, but when once com- 

 pletely buried, they turn in any direction up or down or on the 



* Tentacle Reflex of a Holothurian, Cucumaria pulcherrima. Johns Hopkins Univ. 

 € , irciilars, No. 5, pp. 24-27, 1905. 



t Bull. U. S. Fish Commission, page 25, 1899. 



