WORMS 175 



common near shore, and one, at least, is found on the 

 high seas north and west of Britain (Arachnactis, 

 Fig. 101). 



The group known as Ctenophora, from their comb- 

 like paddles, is common ; Pleurobrachia (Fig. 102) may 

 be taken off our own coasts ; with its two graceful ten- 

 tacles, it plays its prey exactly as an angler plays a 

 salmon. Cestus, or Venus's girdle (Fig. 156), is an 

 inhabitant of warmer seas. Beroe (Fig. 97), a glove- 

 finger of pink jelly, also occurs off our coasts. 



The various groups of flatworms are rarely met with 

 in Plankton, and consequently should be carefully pre- 

 served if found. But the group of roundworms 

 (Chaetopoda), to which belong the common earthworm, 

 and the ragworm and lugworm beloved of sea-anglers, 

 require mention. Near shore swimming larvae, which 

 ultimately grow into crawling or burrowing adult 

 worms, are frequent at some seasons ; Fig. 104 shows 

 some of the simpler forms. Many are provided with 

 long bristles, such as give the name to this group 

 (" bristle-feet "). Of adult forms, perhaps the com- 

 monest isTomopteris (Fig. 103), sometimes 2 inches long. 

 Of the Nereids or ragworms, some are occasionally cap- 

 tured near shore, apparently at the breeding season. 

 Of the curious Syllid worms (Autolytus) some repro- 

 duce asexually by forming a second or even several 

 heads in the course of the body, and then dividing into 

 as many worms as there are heads. 



Of the wheel- animalcules (Rotifera), so common in 

 fresh water, some seventy species are stated to be 

 marine ; little is known of them. 



The little glass-arrows, or Chsetognatha, are of con- 

 stant occurrence, apparently in all seas ; they vary in 

 length from J inch to 4 inches (Figs. 105, 106). 



The group to which crabs, lobsters, and so forth 



