The parchnifiit worm CImetopterus lives in a U-shaped 

 tube in muddy bottoms. Its bizarre paired paddles 

 pump through the tube a current bringing oxygen and 

 food, and help manipulate the mucus bag with which 

 food particles are trapped. ( Massachusetts. George G. 

 Lower ) 



After a few minutes the whole headgear emerges 

 slowly, mushrooming to a diameter of perhaps 3 

 inches like the cloud from an erupting volcano. Cilia 

 covering the surfaces of the gill plumes then begin 

 driving water against them. Any food particles are 

 trapped in a mucus film carried down channels to the 

 mouth. 



Serpulids (Plate 82) are mostly smaller worms, 

 with gill plumes seldom over Vi of an inch across. 

 They have gone one step further than the feather- 

 duster worms in that one part of the gill plumes has 

 become a "stopper," pulled into place in the tube 

 opening like a cork in a bottle as the worm jerks back 

 into the security of its shelter. 



Serpulids build limy tubes that coil or spiral. Spi- 

 orbis attaches to seaweeds a white, snail-like shell, 

 often no more than Vs of an inch across. Hydroides 

 and Serpula range widely, often to moderate depths, 



usually attaching their larger and irregularly coiled 

 tubes to the shells of large moUusks. 



A few exceptional polychaetes live in fresh water. 

 Largest of these is Nereis Umnicola, found in lakes 

 and streams of California, close to the Pacific Ocean. 

 Others inhabit remote Lake Baikal in Siberia. Even 

 better known is the tiny, gill-bearing Maiiayiinkia 

 discovered in a Philadelphia suburb but now known 

 also in the Great Lakes, where it builds tubes attached 

 to stones. Its blood contains a green pigment (chloro- 

 cruorin) rather than the red hemoglobin found in 

 most other annelid worms. 



Some minute worms, all of them less than '/s of an 

 inch in length, as adults resemble juvenile stages of 

 polychaete worms. For years they were suspected of 

 being "'missing links" and received the name "archi- 

 annelids." Now it appears that they are merely de- 

 generate types. Each of them has but five or six seg- 

 ments and develops neither parapodia nor bristles. 

 On the dorsal surface, bands of cilia mark the bound- 

 aries of the segments; the ventral surface is rather 

 uniformly ciliated. Some species are transparent, 

 others bright orange or translucent white. Polygor- 

 dius is almost as slender as a hair, and is a salmon- 

 pink; it lives under stones on both sides of tlie North 

 Atlantic and in the Mediterranean. Dinophilus is 

 more oval in outline, and occupies similar sites 

 around the world. 



The Bristle-footed 



Annelids 



(Class Oligochaeta) 



An earthworm maintains its grip upon the soil with 

 the bristles that give the class Oligochaeta its name 

 (from the Greek oligos, small, and chaeta, a bristle). 

 Each segment of the animal has four pairs of glassy 

 bristles which can be detected as roughnesses when a 

 finger is rubbed along its sides or undersurface. 



The worm has muscles with which to tilt the bris- 

 tles forward or back, and it uses this simple control 

 to determine whether the alternate contractions and 

 extensions of its body will shift it ahead or toward the 

 rear. If an earthworm tilts the bristles to slant back- 

 ward and extends them to catch upon the soil, it is 

 ready to move forward. The bristles then permit any 

 portion of the worm to slide ahead, but prevent it 

 from slipping backward. If the worm tightens its lon- 

 gitudinal muscles and shortens itself, the anterior end 

 of the body holds to the creeping surface while the 

 posterior end skids forward. When the worm con- 

 tracts its encircling muscles and relaxes the longitu- 

 dinal set, its body lengthens. The bristles in the pos- 

 terior segments hold fast while those in the anterior 

 region slip easily, and the worm moves ahead. 



204] 



Fan worms (sabellids) are annelids that extend from their parchment-like 

 tubes a lovely crown of feathery tentacles with which suspended food particles 

 are gathered and oxygen obtained. (Bimini. Fritz Goro: Life Magazine) 



