VERMES. 183 



plish-black bristles, with a bronze iridescence. It has 

 eyes, tentacles, and a proboscis which can be pro- 

 truded. All the Errantia are carnivorous, and hunt 

 for their food. The Tuhicolce (tube-dwellers), as their 

 name implies, mostly secrete a house for themselves. 

 They include some of the most familiar marine worms 

 — Terehella, which builds itself a tube cemented 

 of sand and shells; Pectinaria, so called from its 

 comb-like gills, which builds a tube of' grains of 

 sand only ; Spirorbis, which secretes the minute 

 coiled tubes, like univalve shells, which are often seen 

 attached to tangle and other seaweeds ; the Serpula, 

 which secretes larger snake-like tubes, found in 

 multiple masses on shells and stones ; Sabella, which 

 is much larger, with a tube not so much twisted. The 

 last two are very pretty objects when their heads, 

 with their bright-coloured branchial filaments, are 

 protruded from the tubes. Arenicola, the lob-worm, 

 which burrows in sand, is nearly related to them ; but 

 the gills are not on the head, but further down the 

 body. It has no tube. The OUgochoita, another order 

 of the Chsetopoda, ai-e familiarly represented by the 

 common earthworm. The small delicate-looking 

 worms found in mud are a nearly allied form, called 

 Nais. The earthworm is the animal usually chosen 

 for description as a type of the more highly developed 

 members of the group Vermes (see p. 132). The 

 body consists of a series of rings or segments. The 

 mouth leads by a muscular pharynx to a well-differen- 

 tiated alimentary canal, lying in a body-cavity. ' The 



