cm 



slightly pointed. The head pore is present at o/I. The anterior 

 four or five intersegmental grooves are distinct, but beyond this 

 region they are obscure. Three to eight secondary transverse grooves 

 occur on all of the somites posterior to II or III with the exception 

 of XII and XIII. 



A conspicuous feature of living specimens is the presence of 

 definitely arranged spots on the external surface. They are disposed 

 in transverse rows, 2-3 per somite, each row containing 2-4 spots. 

 One row is slightly anterior to the seta?, another slightly posterior 

 to them, and a third caudad to the latter. These markings do not 

 appear in alcoholic specimens. 



Scfcc. — The setcT are slightly sigmoid, but in an examination of 

 the living material or of specimens mounted in fofo it is very easy 

 to overlook their slightly sigmoid form and to mistake them for 

 straight setcC. Transverse sections of the W'Orm (PI. CII, Fig. 31) re- 

 veal the curves distinctly. The setne are arranged in four bundles 

 per somite, two ventral and two lateral. The number of set?e per 

 bundle varies from 2 to 4. In the anterior region the numbers 4 

 and 3 seem to predominate, while in the posterior region there are 

 usually 3 per bundle, and but 2 in the last one or two somites. The 

 distal extremities of the seta? of each bundle are all curved in the 

 same direction, those of the lateral bundles curving ventrad and 

 those of the ventral bundles curving dorsad. The proximal ends of 

 the setae also show a slight curvature in a direction opposite to that 

 of the distal portion. 



Cuticula. — There is a very thick resistant cuticula of which the 

 thickness is about equal to that of the combined thickness of the 

 hypodermis and the muscular layers of the body wall. This cuticula 

 is so resistant that in some cases it caused considerable trouble in 

 sectioning. It appears to be approximately uniform in thickness 

 throughout the length of the body. 



INTERN.VIv CHARACTERS 



Lymphocytes. — The lymphocytes are scattered sparingly through- 

 out the greater part of the coelom. They are nucleated and the 

 cytoplasm is granular. The shape varies from an oval to a decidedly 

 oblong form, and the length of some lymphocytes is about twice that 

 of others (PI. CI, Fig. 30). 



Brain. — The brain lies in I, II, and III, chiefly in II. Its length 

 f PI. CII, Fig. 32) is approximately twice the greatest width. The 

 anterior margin is decidedly conical; the posterior margin is con- 

 spicuously emarginate; and the lateral margins converge anteriorly. 



