394 HOMES WITHOUT HANDS. 



have been constructed by other creatures, but making them 

 gradually, and in some instances, getting together sand, stones, 

 umd, shells, and other objects, which they use as materials 

 for their homes. We may call the caddis grubs, which have 

 recently been described, the tubicolous larvae of fresh water, and 

 very curious are the habitations which they construct. In salt 

 water, however, there is much more variety than in ponds and 

 rivers, and the tubicolse are many and diversified. 



We will begin with those which are most plentiful, and which 

 are best known, because. the hardness of their tubes causes them 

 to be preserved long after the inhabitants have perished. If the 

 reader should happen to have used a dredge, or a trawl, he must 

 have brought to the surface great numbers of white shelly tubes, 

 some of them being nearly triangular, and adhering by their 

 whole length to a stone or a shell, and others nearly cylindrical, 

 and rearing themselves from the stone after the first half-inch 

 or so. 



These are the work of a curious worm, called by Linnaeus the 

 Serpula, on account of the serpentine manner in which its tube 

 is formed. There are many species of Serpula, and some of the 

 more conspicuous among them will be mentioned. 



The Serpula belongs to the Annelidas, or Einged animals, a 

 very large group, which includes the earthworm, the leech, the 

 nereis, and many otber well-known creatures, all of which 

 have the body composed of a great number of rings, and are 

 destitute of true feet. They breathe either through the skin, 

 by sacs, or by gills, and in the present genus, the respiration is 

 by means of gills, which are always delicate and elegant in form, 

 and mostly brilliant in colour. The body of the Serpula is com- 

 paratively short, the tube being frequently six or ten times as long 

 as the animal which made it, and in consequence the Serpula 

 possesses a deep and safe retreat, into which it can withdraw 

 itself whenever threatened by danger. 



The verj'^ fact, however, that the worm lives in a tube, causes 

 the observer to ask himself how the creature contrives to breathe, 

 and how the long tubular shell is kept clean. A reference to 

 the illustration will explain the former of these difficulties, and 

 the latter will presently be touched upon. 



Projecting from the orifice of the shell may be seen a curious 

 fan-like appendage ; were the illustration to be coloured, this 



