ALASKA NEMERTEANS 43 



Nareda suferha as having but a single pair of rounded ocelli situated 

 wide apart on the transverse white band of the neck. It seems highly 

 probable, as Verrill suggests,' that both of the species are identical ; 

 in the one case only the marginal eyes were seen, while in the other 

 the cerebral clusters were supposed to represent single eyes and the 

 marginal ones were overlooked. Verrill ' describes the eyes correctly, 

 and his diagnosis of the species is so full and accurate that it is neces- 

 sary to describe here the internal anatomy only. A pair of elongated 

 clusters of ocelli lies on the antero-lateral margins of the head, and an- 

 other smaller cluster on, or near, the angular white spot on each side 

 of the head. As shown in fig. 10, each of the anterior clusters may 

 contain upwards of 20 ocelli arranged in two or more irregular rows 

 nearly parallel with the antero-lateral margin of the head, while the 

 posterior groups may consist of 8 to 15 similar ocelli. The posterior 

 groups are situated deep in the tissues of the head. Of course the 

 number of ocelli varies greatly in different individuals. 



Cerebral sense orgatis. — Well developed. They lie a little in front 

 of the brain, beside the esophagus, and below the cephalic blood 

 lacunar. Each sense organ has a wide canal which leads a short dis- 

 tance anteriorly and opens to the exterior on the latero-ventral aspect 

 of the body. The brain itself is of large size, with a thick ventral 

 and narrow dorsal commissure (p1. xi, fig. 2). 



Nephi-idia. — The nephridia extend from near the brain (pi. xi, 

 fig. 2) well backward in the esophagal region. In one specimen there 

 were two pairs of efferent ducts opening on the latero-ventral aspect 

 of the body ; in another only one pair. 



Cephalic glands. — The cephalic glands open on the tip of the snout 

 and are well developed. Sub-muscular glands, likewise, are remark- 

 ably abundant. They reach from the brain region well back towards 

 the end of the esophagus. They are multicellular, each one being 

 composed of upwards of a score of large, vacuolated cells with small 

 nuclei situated on the side farthest from the lumen. Each gland has 

 a twisted duct leading through the muscular layers, basement membrane, 

 and integument, and opening to the exterior on the ventro-lateral aspects 

 of the body (p1. xi, fig. 2). 



Beneath the esophagus a broad caecal appendage of the intestine 

 stretches forward well toward the brain region. This ctecum consists 

 of a large median canal with pouch-like diverticula extending dorsally 

 above the lateral nerve cords. 



There is the usual anastomosis of the three longitudinal vessels, and 



» Marine Nemerteans of New England, Trans. Conn. Acad., viii, p. 12, 1S92. 



