238 ITS STRUCTURE AND HABITS. 



five longitudinal colourless lines, of wliich tlie dorsal 

 ones are only half as broad as the ventral. Under 

 a lens the ground colour is resolved into a number of 

 minute red dots, thickly placed dorsally, and often 

 becoming confluent into longitudinal dashes, but 

 placed thinly on the belly. 



The anterior extremity forms a disk surrounded by 

 a marginal circle of twelve short tentacula. These 

 organs are rather thick columns, with their bases in 

 contact, tapering to the tip, where each branches into 

 four short diverging fingers, which are likewise taper 

 and pointed. The red speckling extends up the 

 tentacles. The mouth is a cup-shaped circular cavity, 

 whose edges reach to the bases of the tentacles. 



The dental cylinder of the Holothurice is represented 

 by a slender ring of minute white calcareous pieces, 

 varying in size, and irregular in form. None of them 

 are larger than -gV^h of an inch square. They are 

 imited by cartilage into an elastic ring, running round 

 the base of the tentacular circle. 



While in captivity the motions of these animals 

 were quite vermicular, slowly twisting the long body 

 into knots and contortions, and writhing about. The 

 tentacles were now and then bent inward to the 

 mouth, one or two at a time, and then unfolded. They 

 did not long retain the cylindrical form in which I 

 received them ; very soon one after another began to 

 constrict the body into knobs at irregular intervals, 

 occasionally so forcibly as to separate into two or 

 many pieces. Sometimes the division was incom- 

 plete ; so that the intestines, and especially the long 

 generative threads, were forced out abundantly from 



