BY VERA A. IRWIN-SMITH. 



795 



Fig.41.— C/i. hasweUi. 



Lateral view of dorsal seta? and glands {yJ) in 



the head; ( x 400). 



nature. The thickenings on the strands seem to suggest nerve- 

 matter, but I think it moi-e probable that they are glandular in 

 character, and secrete a fluid which assists the hollow, dorsal 

 set?e in their locomotory function. 



Another body, of a glandular character, lies in the posterior 

 end of the trunk, ^^^ ^^^ 



just dorsal to the 

 rectum. It is club- 

 shaped, composed of 

 several, large, finely 

 granular cells con- 

 taining numerous va- 

 cuoles and large nuc- 

 lei, and is bounded 

 by a distinct wall 

 (Figs.27, 36-39, ^.(/.). 

 It is connected with 

 a fine duct, which runs back through the tail, and opens by a fine 

 pore at the posterior extremity. Large, bright drops of fluid 

 are distinguishable in the duct, in some specimens; it seems pro- 

 bable that this organ is an excretory 'tail-gland.' 



In the male, the reproductive apparatus consists of a single 

 cord, which begins at a distance of 0*074 to 0'140mm., from 

 the neck, and extends straight back below the alimentary canal, 

 to open with it at the anus. The anterior portion is solid, and 

 terminates in a fine point (PI. xlvi., t.). It has an average width 

 of 0*007 mm., and consists of a closely packed mass of small cells 

 enclosed by a firm wall. Further back, the cells become 

 larger and more loosely arranged, and take on the definite char- 

 acter of sperms, of rounded or somewhat irregular shape, with 

 fragments of connective tissue between them (Figs. 42-43, 45). 

 This portion, which has a width of 0*014 mm., passes abruptly, 

 towards the middle of the body, into a definite tube, with very 

 wide, cellular walls (Fig.44, v.s.). The lumen is extremely small, 

 and, in cross-section, is surrounded by four or five, large cells, 

 with very large nuclei. In longitudinal section, it has the ap- 



