CHARACTERISTIC DEEP-SEA TYPES. WORMS. 57 



It is interesting to find that the Serpulidae (Fig. 272) also 

 occur at great depths, because Ehlers, in working up the an- 

 nelids of the "Porcupine" expedition, had no- 

 ticed their absence in deep water, and left it 

 undecided whether they were excluded by the 

 peculiar nature of the bottom or by the low tem- 

 perature of the deep sea. But it 

 is not uncommon in the deep water 

 of the Gulf of Mexico to bring up 

 rocky fragments which, judging from 

 the amount of mud brought up by 

 the trawl at the same time, must 

 form isolated patches, and in these 



Fig. 272. Pomalo- 



stegus steiiatus. f. undoubtedly the oerpulse thrive. 

 (Fig. 273.) Terebellidae and Serpu- 

 lidae have been obtained by the " Challenger " at 

 depths of nearly 3,000 fathoms. Of course, where 

 the tubes are composed of secretions, as in Hyali- 

 ncecia, they are independent of their surroundings 

 and of the character of the bottom. But the Fig m 

 majority of the tube builders depend upon the Hyaiopomatus 

 material at their disposal, using, to strengthen their x 

 tubes, either sand, or mud, or larger solid particles, such as 

 foraminifers, bivalves, sponge spicules, and the like. 



