164 COB 



municate with the exterior pass anteriorly and ventrally to open on the 

 latero-ventral aspects of the head, as usual. 



Reproductive Organs. — Sexual products were found to be nearly 

 mature early in September, but none of the eggs could be made to de- 

 velop at this time by artificial fertilization. They are probably usually 

 discharged late in September or in October. The sexual glands do 

 not extend forward as far as the opening of the esophagus into the in- 

 testine, as they do in many related species. They are surrounded by 

 a considerable amount of parenchyma, except when fully mature. 

 The genital ducts were preformed as far as the basement layer of the 

 body walls during the latter part of August. These ducts all open on 

 the dorsal surface of the body, although in the male some of the sper- 

 maries are situated ventral to the lateral nerves. In such cases a long 

 duct from each spermary passes internally to the nerve to open through 

 the body walls above the lateral margin, as in the case of the glands 

 situated dorsally. 



Habitat. — Among algse between tides. Pacific Grove; common. 

 On piles of wharf , Monterey ; abundant. In similar situations, San 

 Pedro Harbor; not common. Collections of bryozoa and small algae 

 from piles at Monterey always furnished many specimens of this con- 

 spicuous, but variously colored species when left standing a short time 

 in sea water. As noted above, these worms are very hardy, moving 

 about actively for several hours after the pigmented integument has 

 been sloughed off. When placed in formalin they do not break up 

 spontaneously, but usually die intact and well extended. 



II. TETRASTEMMA BILINEATUM sp. nov. 

 p1. XIV, fig. 6 ; p1. XXI, figs. 13, 14 ; pi. xxii, fig. 4. 



A minute species, measuring when sexually mature only 5 to 10 

 mm. in length, and less than a millimeter in diameter. Body rounded 

 throughout, of moderate proportions, but rather shorter and stouter 

 than in many related species. Head of moderate size, provided with 

 two pairs of faintly -marked oblique grooves, but not distinctly sepa- 

 rated from the parts following. 



Color. — General color of body flesh color, creamy, or grayish, 

 with two very conspicuous deep brown stripes extending along the 

 dorsal surface nearly the whole length of the body. The longitudinal 

 stripes are sometimes reddish brown and sometimes deep chocolate. 

 The ventral surface is mainly grayish. Anteriorly the stripes ter- 

 minate somewhat in front of the ocelli, but sometimes reach the very 

 tip of the snout. Posteriorly they extend nearly, though not quite, to 



