74 COE 



ing lies at the outer end of the oviduct on the dorso-lateral aspect of 

 the body. The bodies of many of these worms were so distended with 

 sexual products that they were very easily ruptured and could conse- 

 quently be preserved intact only with great care. 



Size. The length of this species is commonly about 150 mm. in 

 extension, although several individuals were found which were more 

 than 300 mm. long. 



Habitat. The species was found under stones between tides in 

 rather muddy localities at New Metlakahtla on Annette Island, at 

 Glacier Bay, Sitka, Yakutat, and at Orca and Virgin Bay in Prince 

 William Sound. At the four last-named localities the worms were 

 abundant. Nearly 50 individuals, some of them nearly 300 mm. long, 

 were found at Sitka massed together in a single cavity in coarse 

 gravel mixed with mud. All were filled with fully mature sexual 

 products, and the bodies of nearly all were in contact in a tangled 

 mass. 



Cerebratulus Renier. 

 Prospetto della Classe dei Vermi (t. Burger), 1804. 



The species of this genus are distinguished by long, flattened bodies, 

 the lateral margins of which are thin, adapted for swimming. Most 

 species are very active, swim readily with undulatory motion, can roll 

 up spirally and become twisted, but are only moderately contractile in 

 length, and do not draw together into a tangled mass. The dorso- 

 ventral musculature is highly developed, as are likewise the longi- 

 tudinal and oblique muscles. 



Head usually pointed anteriorly, but very changeable in shape; 

 lateral slits long and deep ; proboscis pore terminal ; mouth large, and 

 situated behind the ganglia ; esophagal region mostly rounded ; intes- 

 tinal region broad and flat with thin lateral margins ; the posterior end 

 extremely flattened and provided with a delicate caudal cirrus, which 

 extends beyond the opening of the intestine, and in most species is easily 

 broken off and lost. Eyes usually wanting ; body commonly of a nearly 

 homogeneous color without distinct markings (such as longitudinal and 

 circular bands and rings) . 



Proboscis sheath reaches to posterior end of body ; proboscis very 

 long and strong. Intestinal pouches deep and mostly forked peripher- 

 ally ; central intestinal canal narrow. Neurochord cells probably com- 

 monly present in brain and lateral nerve cords, though they have as yet 

 been found in but few species. 



