NEW SPECIES OF XEMEKTEAN. 



121 



Zygeupolia litoralis, and certain other Heteronemerteans, it is not 

 unlikely that the retractor muscle is absent. Only two layers of 

 muscles are present in the proboscis, a longitudinal layer on the 

 outside and a circular layer within --the inner longitudinal layer 

 found in many species of the genus being entirely wanting. In- 

 side the muscles occur the usual nervous plexus and the connec- 

 tive tissue layer situated beneath the inner glandular epithelium. 



FIG. 2. Portion of transverse section through head in region of dorsal brain com- 

 missure (dc) and attachment of proboscis ( />) to tissues of head. The two highly de- 

 veloped proboscis nerves (/) are just on the point of entering proboscis. The dis- 

 position of the cutis glands (cgl) and their absence beneath the cephalic furrow, the 

 relations of the cephalic blood lacunae (cl] and the cephalic musculature are shown; 

 i, integument ; i;/i, integumental muscles ; re, rhynchodaeum ; t/i, cephalic muscles. 



Dorsal and ventral muscular crosses are well developed in this 

 species. 



All three of the muscular layers of the bod}' walls are well de- 

 veloped. In the posterior portion of the body alone is the inter- 

 nal longitudinal muscular laver verv much reduced. 



o / J 



In regard to the alimentary canal it should be remarked that 

 the esophagus may be differentiated histologically into an anterior 

 and a posterior chamber, as has been described so fully by Miss 

 Thompson 1 for Zygeupolia. The anterior chamber, or esophagus 



1 L. <-., p. 706. 



