SIPHON- WORMS. 



55 



FlG. 50. HOLOTHURI^E. 



are capable of being withdrawn into the body, but are commonly protruded 

 in' expectation of prey, which is seized and dragged to the mouth by thesi* 

 appendages. They greatly resemble in appearance the tentacles of some of 

 the Actinia?, especially when the Holothuria has buried 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 (Holothuria r), sometimes called the "Nigger," is 

 very common in deep water off the coast of Cornwall : it is held by the fishermen in 

 great detestation, on account of its slimy appearance, and from an idea that where the 

 "Niggers" are numerous and get into the crab-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 lengthened and 



slender body, and all the aspect of worms, 

 with the exception of the circle of tentacles 

 around their mouths, by which they indi- 

 cate their lingering affinity to the Echino- 

 derms. They have no suckers or feet, and 

 many species are marked by wrinkles en- 

 circling their body, causing them to re- 

 semble earth-worms in their appearance 

 as well as in their habits. Most of them 

 bore deep holes in the sand, wherein they 

 lodge. Others conceal themselves in the 

 crevices of rocks; and there is one species, 



FIG. SI-HERMIT SIPUHCULUS, Sipunculus Bernhardus, represented m 



our engraving (Fig. 51), which selects the 

 shell of some periwinkle or whelk for its abode. 



Sipunculus, from ffi(f>ov, a tube. 



