Worms. 



57 



vermiform coils ; the wliole underground burrow is U-shaped, and 

 a small, funnel-like hole in the sand, at some distance from the 

 casting, indicates the position of the animal's head. The walls 

 of the burrow are to some extent strengthened by a sticky secre- 

 tion from the bod\' of the worm, but many Polychsetes go further 

 and construct definite tubes, in whicli they dwell. As an 

 example of a tube made exclusive^? of mud and slime, we may 

 mention that of the common Amphilrile johnsioni ; in other 

 worms the tube ma^' be strengthened In' the addition of grains 



71. ANTERIOR EXTREMITY OF AMPHITRITE JOHNSTONI (AFTER 



CUNNINGHAM AND RAMAGE). 



of sand, bits of shells, or even calcareous matter secreted by the 

 animal itself. On turning over stones in muddy places the presence 

 of Ainphiirite (Fig. 71) is often revealed, not by the tube, which 

 is sunk in the mud, but b}' the head of the worm, furnished with 

 a large number of long, slender, reddish filaments, the movements 

 of which attract attention. The first few segments of the body 

 bear gills, somewhat similar to those of the Lug-worm. The 

 Sand-mason Worm, Terehella conchilega, is similar to the pre- 

 ceding, but protects itself by a rudelj' constructed tube of sand- 

 grains and shell debris, cemented together by a special secretion. 

 The tube is easil}' detected on the beach at low tide on account 

 of the peculiar fringe surrounding its anterior opening. 



Pectinaria belgica (Fig. 70) produces, with the same materials, 

 a much more neatl}' finished structure, and the tube is almost 

 cylindrical. The name Pectinaria (from pecten, a comb) 

 refers to the beautiful crown of stiff golden bristles which protects 

 the head, forming a sort of cover to the anterior, slightly wider 

 opening of the tube. The most perfected tube-dwellers among 

 the Polychastes are undoubtedlj? those whicli are grouped 



