NEMERTEANS l8l 



Llneidffi have these glands been found to be so extensive as in the 

 present species. 



Plgjtient. — The peculiar bluish color which appears after the 

 worms have been preserved, and have consequently lost their original 

 pink or reddish color, is due to a vast number of minute granules situ- 

 ated in the nervous plexus which lies immediately external to the 

 circular muscular layer. The granules are present only in that portion 

 of the plexus which lies dorsal to the lateral nerves. 



Proboscis. — The proboscis sheath is remarkably long for the genus, 

 extending very nearly to the posterior extremity of the body. The 

 proboscis is of moderate proportions. In its musculature it exhibits an 

 interesting departure from the type characteristic of the genus. The 

 circular and outer longitudinal muscular layers are of the usual propor- 

 tions, while the internal longitudinal musculature is represented by two 

 bands placed symmetrically on opposite sides of the proboscis. These 

 longitudinal bands occupy about one-sixth to one-eighth of the circum- 

 ference of the internal epithelial layer, which elsewhere borders the 

 inner face of the circular musculature. In thickness the two muscular 

 bands, which represent the inner longitudinal musculature found in 

 most related species, often equal that of the outer longitudinal layer in 

 their middle portions, but are much thinner toward their borders. 

 Back toward the middle portions of the proboscis they become gradually 

 thinner, and more posteriorly eventually disappear, allowing the inter- 

 nal epithelium to border the circular muscles without interruption ex- 

 cept from the nervous layer. Where the two longitudinal bands are pre- 

 sent the proboscis nerves are well developed as a single pair of flattened 

 cords which lie immediately external to those bands, but after the bands 

 disappear, the nerves spread out as a plexus lying between the circular 

 muscles and basement layer of the internal epithelium, as in related 

 species. This peculiar arrangement of the musculature presents a con- 

 dition intermediate between those members of the family Lineidaa in 

 which the three layers are well developed, and those (such as Lineus 

 Jlavescens^ for example) in which the internal longitudinal layer is com- 

 pletely wanting. In the posterior portions of the proboscis only longi- 

 tudinal fibers occur, and these are bounded externally by a thin fibrous 

 layer, and internally by a thin epithelium lining the proboscis cavity. 



Alimentary Canal. — Esophagus divided into two well-marked 



portions, separated by a constriction, and distinguished by differences 



in the epithelial lining similar to those which ^liss Thompson has 



recently described for Zygetipolia (1902).^ The mouth, situated as 



1 Proc. Acad. Nat. Sci. Philadelphia, 1901, p. 709. 



