292 bulletin: museum of comparative zoology. 



Ocelli of medium size ; situated deep in tissues of head ; their 

 position varying greatly according, to the state of contraction of 

 anterior portion of body (PI. 2, %. 26; PI. 18, fig. 113). 



Size. — Commonly about 20-30 mm. long and 1 mm. wide, occa- 

 sionally up to 70 mm. in length and 2 mm. in diameter. 



Proboscis — Proboscis sheath extends to posterior end of body. 

 Proboscis pale, provided with ten conspicuous nerves. Basis of 

 central stylet of the ordinary conical form, with swollen, rounded 

 posterior end, exhibiting considerable variation in size and shape ; 

 central stylet of moderate pi'oportions, not particularly sharj), usually 

 a httle more than half as long as basis. There are commonly three 

 (occasionally two or four) stylets in each of the two lateral pouches 

 (PI. 18, fig. 115). Length of basis varies from 0.11-0.17 mm., and 

 that of stylet from 0.06-0.09 mm. Posterior ])ortion of basis dark 

 and granular, becoming translucent in anterior half (PI. 18, figs. 

 114, 115; Text-figs. 57-59). 



Cephalic glands fairly well developed in head, but not extending 

 back to brain. Submuscular glands wanting. 



Alimentary canal. — Rhynchodaeum remarkably short ; intesti- 

 nal caeca extend forward to dorsal brain lobes, uniting posteriorly 

 beneath the stomach to form a broad median caecum from which 

 other pairs of slender diverticula are given off at intervals, and these 

 pass forward above the lateral nerves and end blindly anteriorly. 



Blood oessels conspicuous in life because of the deep red color of 

 the oval discoid corpuscles. 



Nephridia extend forward as far as brain region, the tubules be- 

 ing largest anterioi-ly, where they ramify in the body parenchyma 

 both above and below the lateral nerves, as well as beside the brain. 

 A single pair of large efferent ducts are situated about on a level 

 with the posterior ends of the dorsal ganglia, and commonly a pair 

 of smaller efferent ducts are found well back in the esophageal 

 region. 



Cerebral sense organs situated ventrally some little distance in 

 front of brain. 



Habitat. — Common among algae between tides. Pacific Grove, 

 Calfornia; abundant on piles of wharf, Monterey ; in similar situa- 

 tions, San Pedro, California. Collections of bryozoans and small 

 algae from piles at Monterey always furnished many specimens of 

 this conspicuous, but variously colored, species when left standing a 

 short time in sea-water. Sexu^ally mature in September. As noted 



