TUBE-MAKERS. 325 



(Terebella textrix), which constructs a semicylindrical 

 sand tube, of insufficient dimensions to cover the 

 body, or receive the head. " A peculiar feature in its 

 history is its producing a real cobweb, as distinct as 

 that of the spider, with which it covers itself, and 

 which also frequently, if not always, serves to support 

 its spawn. The texture is very thin, rather irregular, 

 and composed of the finest threads almost invisible 

 from their slenderness, and extreme transparence. 

 Neither the mode of formation, or extension, nor the 

 expedients for securing their extremities, are obvious. 

 Such a web, from a specimen njne lines long, covered 

 an area fifteen lines square. This is plainly the work 

 of some exertion, as the threads, sometimes amount- 

 ing to fifty, are fixed to the side of the vessel as high 

 above the bottom as equals the length of the weaver, 

 or more ; and they also extend below, there to be 

 secured. Thus it is evidently an artificial work, and 

 it receives successive accessions. The specimen 

 observed continued its work about three weeks in 

 May, but although surviving a month longer, it wove 

 no more." 



Another Tube-forming Annelid (Pectinaria belgica) 

 is found on sandy shores, within the lowest water- 

 mark, which " constructs a very delicate tube ; as thin 

 as paper, exclusively of the grains of sand aggluti- 

 nated together in an extraordinary manner. The 

 thickness of the side does not exceed a single grain ; 



