THE TUBE-MAKERS. 



233 



feet, with two hooked set* and cirri or pimples. There are no blood-vessels. These curious worms 

 live on the surface of Comatulae, kinds of Echinoderms. Their larvae are ciliated all over, and the 

 head and feet develop gradually. Probably the 

 position of the worm is amongst the Polychaeta. 



SUB-ORDER TUBICOL^E. THE TUBE- 

 MAKERS. 



These worms live in more or less solid 

 tubes, which they construct of different sub- 

 stances such as mud and excreted mucus 

 mixed with calcareous matter, grains of sand 

 and pieces of shells. .Some live in mud, or 

 in penetrations in rocks, and others drag 

 their tubes after them. The Tubicolse have 

 a not very distinct head, a short, often not 

 projectable proboscis, and no jaws. The 

 branchiae are either deficient, or are limited to 

 two or three segments behind the head. The 

 exception is in the Lob Worm, where they are 

 placed on the back of the median segments. 

 There are numerous filiform tentacles and ten 

 tacular cirri on the head, and one or more 

 opercula on it. The feet are short; their ac- 

 cessory structures are small, and are of no use 

 in swimming ; but the dorsal lobes of the feet 

 have capillary seta?, and the inferior are pro- 

 jections with hooked seta? or flat hooks. The 

 eyes may or may not be present, and are found 

 in many situations, as are also the branchial 

 tufts, when they are very numerous. The body 

 may be divided into two or three regions, the seg- 

 ments of each differing in their shape and in the 

 kinds of appendages. They are not carnivorous, 

 and are said to feed upon vegetable matter. The 

 long tentacles are of use in building the tubes. 



The development of these worms may be 

 in some instances retrogressive ; organs degrad- 

 ing and degenerating for want of use. In one 

 group (Spirorbis) the eggs and larvae are earned 

 about by the mother in a pouch, and when they 

 are able to construct a tube for themselves 

 they escape. The larvae are mostly free and 

 ciliated, and they gradually lose the cilia, and 

 assume the form of worms, and have feet 

 and tentacles. Some roam about in this state, 

 protected by their membranes, and finally grow 

 eyes and auditory sacs, and begin to reproduce. 



The Tubicolae are divided into numerous 

 families, and a great number of genera, The in- 

 dividuals are excessively numerous, and live at 

 all depths on the sea and ocean-floor. Amongst 

 the most interesting of the families is that* which contains the common Lug O r Lob or Fishing Worms, f 



* Telethusida:. f Artnimla oiscat-n-um. 



268 



LUG \VOKM. 



A, .inHTior extremity of body, showing irimk; n, one of the body-fines, 

 tbowing bramhiiL-. 



