ECHINODEKMATA. 73 



nevertheless, their relationship to the Urchins and Star- 

 fishes is manifestly shown, by their apparatus of locomo- 

 tive suckers, which are of precisely the same structure as 

 those of the Echinus. As if, however, also to manifest 

 an affinity with the Polype forms, there still exists in the 

 Holothuria a circle of branched tentacles, which surround 





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Fig. 50.— holothuria. 



the mouth. These are capable of being withdrawn into 

 the body, but are commonly protruded in expectation of 

 prey, which is seized and ch'agged to the mouth by these 

 api^endages. They greatly resemble in appearance the 

 tentacles of some of the Adinke, especially when the 

 Holothuria has bui'ied its whole body in the mud or sand, 

 with the exception of these branched tentacles, which 

 expand like the petals of a flower. A species named 



The Cotton-Spinner (Iloloihuria Nigra), sometimes called tlie 

 "Nigger," is very common iu deep water, off the coast of Cornwall ; 

 it is held by the lishemien in great detestation, on account of its 

 slimy appearance, and from an idea that where the "Niggers" are 

 numerous, and get into the Ciab-pots, neither crabs nor lobsters are 

 caught. These animals are frequently near a foot in length, and 

 thick in proportion. They sometimes draw themselves up into a 

 kind of ball, and if touched or disturbed, throw out a bunch of 

 white taper threads of great tenacity, that stick to everything they 

 touch, and no doubt constitute a means of defence. 



The Siphon-worms (Sipunculus)* (Fig. 51) have a length- 

 ened and slender body, and all the aspect of worms, with 



* Sipunculus, from (XKpou, a tube. 



E 



