posedly sedentary types, fashions a beautiful slender 

 tube of sand grains cemented together, and drags it 

 over the sea floor like a trailer motorist in his mobile 

 home. 



One of the chronic burrowers, Arenicola marina. 

 is known as the lugworm by fishermen on both sides 

 of the North Atlantic. Other species of the same ge- 

 nus dig homes in the mud flats of the Pacific. These 

 stout animals reach a length of more than 1 5 inches, 

 with extra encircling wrinkles concealing the fact that 

 the bristle-bearing trunk part of the body has only 

 about twenty-one segments. Tufts of bright red gills 

 mark the sides of each of these segments, but are 

 lacking on the more slender, tail-like, posterior ex- 

 tension of the animal. 



Arenicola lacks teeth in its eversible pharynx, but 

 uses the organ as a burrowing tool in the sandy mud. 

 While feeding, the worm engulfs the bottom material 

 almost indiscriminately, swallowing a lump about 

 every five seconds. It continues at this pace for from 

 half a minute to a minute, then rests about twice to 

 three times as long. From a quarter to a third of each 

 day is spent in feeding, with occasional trips to the 

 surface of the mud flat to expel a coil of sand from 

 which the food materials have been digested. 



The presence of Arenicola in a beach can often 

 be suspected from the circular holes at the ends of 

 the tunnels and the neat coils of castings which ac- 

 cumulate and erode into miniature volcanoes around 

 some of the openings. In reproductive season, these 

 worms enclose their fertilized eggs in great tongue- 

 shaped masses of jelly as much as eight inches long, 

 three inches wide and an inch thick, anchored at the 

 small end in the sea bottom while the larger portion 

 flops back and forth with each wave. After the en- 

 closed eggs hatch, the developing worms use the jelly 

 as food and continue to live in the enlarging cavity. 

 Eventually they have more than a dozen segments 

 and are beginning to resemble their parents; at this 

 stage the small worms escape and the jelly disinte- 

 grates. 



The parchment worm Chaetopterus builds a U- 

 shaped tube lined with a tough secretion suggesting 

 sheepskin. At the bend of the U the creature rests, 

 waving its fan-shaped paddles (parapodia) to propel 

 water past its body. The current brings both oxygen 

 and particles of food; the latter are captured in a re- 

 markable bag of mucus secreted by a pair of wing- 

 like parapodia extending to the tube wall near the 

 anterior end of the body. At intervals of about eight- 

 een minutes, Chaetopterus stops pumping water, rolls 

 its mucus net into a ball, and swallows it. Then it be- 

 gins fanning again. Each ball of food contains virtu- 

 ally every microorganism in approximately a cupful 

 of water pumped through the tube. 



Although Chaetopterus rarely leaves the seclusion 

 of its tube, it is a luminous animal. At night the pro- 



The polychete worm Eunice is an active animal, 

 hunting for bits of food among rock crannies and 

 swimming or creeping by means of bristle-bearing 

 paddles on each body segment. (Wimmer) 



truding tips of its parchment tube may glow from the 

 reflected light. No one is sure whether this attracts 

 minute animals useful as food or has some other 

 significance in the life of the worm. 



On mud flats from New England to Georgia, the 

 presence of another tube-builder, Dioputra ciiprea, 

 can be inferred from the conspicuous "chimneys" it 

 constructs. These extensions of the vertical, three- 

 foot tube project several inches above the bottom 

 and are reinforced externally with bits of shell, plant 

 debris, and seaweed fragments. The worm itself may 

 be 1 foot in length, V2 of an inch in diameter. While 

 covered by quiet water it extends from its tube a 

 strikingly handsome pair of scarlet gill plumes, each 

 treelike, with whorl after whorl of branches arising 

 from a pulsating spiral central stem. 



Tide pools and wharf pilings are home to some of 

 the most spectacularly beautiful polychaetes, the 

 feather-duster worms (Plate 81 ). Many of them are 

 known more correctly as sabellids. They build tubes 

 as much as eighteen inches long, and from the open 

 end extend a pair of stubby, armlike organs (palps), 

 each bearing a spray of gaily banded, feathery gill 

 plumes which serve also in trapping food. In many 

 cases the worm detects the merest shadow falling on 

 the plumes, and snaps back out of sight into its tube. 



[203 



