COE: NEMEKTEANS OF WEST AND NORTHWEST COASTS. 155 



The species belonging to this gemis show a remarkable specific 

 variation in the general shape and size of the body. Some are 

 characterized by extremely long, slender, flattened, and much 

 twisted bodies, while others are short, thick, and cylindrical. In 

 all the species, however, the snout in life is rounded in front and is 

 sharply marked off from the parts immediately following by lateral 

 constrictions. Horizontal furrows are wanting, but small, oblique 

 or transverse grooves may be present on the head. In strong con- 

 traction the esophageal region becomes greatly swollen, the head is 

 drawn in so that the anterior end of the body is large and sharply 

 truncated. 



Proboscis sheath and proboscis short, seldom reaching more than 

 one third the length of body. Proboscis opening subterminal, 

 minute. Mouth a small round opening on the ventral surface 

 immediately behind the ganglia. 



Muscular layers of body composed of a thick outer longitudinal, 

 a circular, and a less thickened inner longitudinal layer. Outside 

 the muscular layers is a well developed cutis, composed of a thick 

 inner layer of connective tissue and an outer layer of glandular 

 tissue. The external epithelium is thin, as compared with the other 

 layers of the body, though the fibrous layer separating it from the 

 cutis is well developed. The musculature of the proboscis consists 

 of an inner longitudinal and an oiiter circular muscular laj'er. Con- 

 sequently there can be no muscular crosses; 



The cephalic glands are enormously developed. They stretch 

 backward on all sides beyond the brain, and even reach some dis- 

 tance into the esophageal region. 



The lateral nerves lie immediately outside the circular muscular 

 layer. There are three longitudinal blood vessels. 



Ocelli are usually present in great numbers, though very small. 



The worms are sluggish in their habits, are unable to swim, and 

 usually show great irregularities in the diametey of the body. They 

 are prone to twist themselves in sharp coils, or in knots, and often 

 lie in lumps. They are usually capable of contracting and extending 

 their bodies to a remarkable degree. 



Three species of this widely distributed genus are represented in 

 these collections. One of these forms has been found only on the 

 coast of Alaska and in Puget Sound, the second is known only 

 from the coast of California, while the third has as yet been col- 



