622 



INTKRNAI, CHARACTi;RS 



Body Wall. — The hypodermis contains unicellular flask-shaped 

 gland cells (PI. XCIX, Fig. i6) which are numerous and generally 

 distributed. They occur among the ordinary hypodermal cells, and 

 each opens at the surface through the distal narrowed neck region. 

 They are much larger than the hypodermal cells though shorter. They 

 are approximately uniform in shape except in the thickened region of 

 the first somite and the prostomium, where they are more elongate. 

 The contents show a certain degree of polarity. In the ectal part 

 of the cell the contents are of such a nature that they stain only 

 slightly, while the opposite end is filled with material which stains 

 deeply. The latter also contains a conspicuous nucleus. 



Brain. — The brain (PI. XCIX, Fig. 15) lies entirely in II and is 

 about one fifth longer than wide. The anterior margin is concave; 

 the posterior margin is convex ; and the lateral margins are gradually 

 convergent anteriorly. Two pairs of supporting strands connect the 

 lateral margins of the brain with the body wall. 



Peptonephridia. — A pair of these organs open into the ventral 

 side of the digestive tract in IV. Each is composed of several 

 branches which arise from a common base, and most of which are 

 directed caudad and terminate in VI. Secondary branching exists 

 to some extent. 



Chyliis Cells. — The chylus cell region is that part of the intestine 

 included in XV-XVII. The chylus cells (PI. C, Fig. 18) are flask- 

 shaped, and each cell contains the characteristic intracellular canal, 

 which has a somewhat sinuous course, especially in the ectal end of 

 the cell. The canal is ciliated throughout almost its entire length. 

 There seems to be no special modification of the cytoplasmic layer 

 surrounding the canal, such as exists in F. firina and some other 

 species. Each cell contains a conspicuous nucleus, which usually lies 

 in the chief bend of the canal. Between the apical ends of the chylus 

 cells are fitted the wedge-shaped ental epithelial cells. The location 

 of the chylus cells in XV— XVII is different froni that in any other 

 species in which they have been described and may, in accordance 

 with the general view of Eisen, be a valid specific character. 



Nephridia. — The first pair of nephridia are connected with V/VI. 

 The anteseptal and postseptal parts (PI. C, Fig. 17) are about equal 

 in size. The efferent duct arises from the mid-ventral surface of the 

 postseptal part, near the septum, and opens to the exterior slightly 

 anterior to the corresponding ventral setae. The lumen is tortuous 

 throughout its whole length. 



