vn ANNELIDA 85 



projecting from the upper end (Fig. 40) ; these may often be 

 seen on a sandy shore above low tide mark, the upper part only 

 of the tube projecting vertically above the surrounding sand. 

 It is interesting to watch these tubes being formed : the particles 

 are seized by the delicate tentacles of the worm and passed 

 into the mouth, where they are moistened by a secretion, and 

 then placed in position at the margin of the tube by the 



B A 



FIG. 39. The Mud Mason (Terebella (Leprea) lapidaria) x . 



A, The worm retracted within the sandy case of a Pectinaria ; B, worm removed 

 from the case, showing the long tentacles, the three pairs of branched gills, and 

 the parapodia (bristle-stumps) down each side of the body. 



tentacle, helped by the lower lip of the worm. Terebella 

 (Lepi-ea) lapidaria forms mud tubes which lie horizontally 

 under stones. The Terebella in Fig. 39, having been turned 

 out of its own case, had taken up its abode temporarily in 

 the tube of a Pectinaria, an unusual occurrence. In each 

 species the body may be entirely withdrawn into the tube, 

 but when undisturbed there project from it three pairs of 

 bright-red branched gills, which are attached to some of the 



