184 THE SEA SHORE 



and occasionally we meet with tubes constructed of the silky secre- 

 tion of the body with hardly any foreign matter. 



We sometimes see edges of rocks, on low, sandy shores, covered 

 with what appears to be large masses of consolidated sand, full of 

 holes a little more than an eighth of an inch in diameter ; and these 

 masses are often so extensive and so firm that they seem to form 

 the greater part of the rock itself. Such masses are particularly 

 abundant on the south coasts of Devon and Cornwall, but are more 

 or less plentiful on most sandy shores of Great Britain. They 

 consist of the tubes of a species of the marine worm Sabella, which 

 have been built up much in the same manner as those of Terebella, 

 but usually exist in such numbers in the same spot that, together 

 with the sand that has been washed between them, they form the 

 dense masses just described. 



A cluster of some dozens of these tubes may be detached with 

 the aid of a hammer and chisel ; or, in some instances, where the 

 mass of tubes is not held so firmly together, by the mere pressure 

 of the hand ; and it will then be observed that each tube consists 

 of a flexible membrane, of a somewhat leathery nature, formed by 

 a sticky secretion from the body of the worm, with its outer surface 

 covered with grains of sand. The tubes may be easily opened, and 

 the occupants extracted for examination, when it will be observed 

 that the front or upper portion of the worm is short and thick, while 

 the hindmost portion is much thinner, and is doubled forwards in 

 the tube. The body is also provided with numerous bristles, by 

 means of which the worm is enabled to grasp the membranous 

 lining of the tube, and thus secure a firm hold within its home. 



A cluster of these tubes should be placed in a rock pool, or in 

 the marine aquarium, when the worms may be seen to protrude 

 gradually, and expose a large number of feathered tentacles, which, 

 by their incessant motion, keep up the constant circulation of the 

 water for the purpose of respiration as well as to bring food particles 

 towards the mouths of the worms. 



It is possible to keep these worms alive for some time in the 

 aquarium, but special care is required for the reason that it is a very 

 difficult matter to secure a cluster of tubes without injury to a 

 certain number which are sure to be broken or otherwise damaged ; 

 and these, dying and decomposing within their homes, speedily 

 pollute the water. Hence it is necessary to keep a sharp watch for 

 dead specimens, which should, of course, be removed at once. The 

 presence of a putrefying worm may often be detected by the 



