MARINE WORMS 



183 



that are constructed by the larvae of caddis flies in fresh-water 

 ponds and streams, and perhaps has noticed the ease with which 

 these creatures may be made to construct new homes after 

 having been turned out of doors. Similar experiments may be 

 performed with Terebella ; for when the worm has been extricated 

 from its tube without injury a work that requires great care on 



account of the soft and slender nature of the creature's body and 



placed in the aquarium with a bed of suitable material, it will build 

 itself a new dwelling. As with 

 the caddis larvae, the different 

 species may be known by the 

 materials they select to construct 

 their tubes, but in captivity they 

 may be compelled to employ 

 other than their favourite sub- 

 stance for this purpose. It is 

 unfortunate, however, that Tere- 

 bella is a nocturnal builder, and 

 thus its movements are not so 

 easily observed. 



When removed from its tube 

 its first movements suggest a 

 resentment at the untimely ejec- 

 tion. This being over, it seeks 

 a sheltered situation beneath the 

 edge of a stone, and, at nightfall, 

 commences the slow process 

 of the construction of a fresh 

 home. The particles of material 

 at hand are seized by the ten- 

 tacles, placed in position round 



the body, where they are held together by the sticky secretion 

 already mentioned. 



The tentacles are employed in two distinct ways : They may 

 be flattened into slender ribbon-like structures, which, by being 

 folded longitudinally at any point, may be made to grasp a particle 

 of sand ; and, in addition to this, the tip of the tentacle may be con- 

 verted into a minute cup-shaped sucker by the withdrawal of the 

 fluid it contains into the body. 



Some species of Terebella build their tubes of ordinary sand, 

 while others select fragments of shells. Some employ mud only, 



FIG. 12Q.~Terebella REMOVED 



FROM ITS TUBE 



