155 



opaque and whitish. The intersegmental grooves are obscure for al- 

 most the entire length of the body ; only the first two or three 

 being at all distinct. In nearly all of the specimens examined the first 

 intersegmental groove is deeply marked. The number of somites is 

 variable, the extremes in a count of nine specimens being 43-55. The 

 prostomium is short and slightly angular at the extremity. The de- 

 gree of this angularity is slightly variable, but all of the specimens 

 show it to some extent. The clitellum is moderately developed and is 

 situated on 5^ XI-)4 XIII. The number of setae per bundle varies 

 in the different regions of the body and to a limited extent in the 

 different rows. In general there are 3-6 per bundle in the ventral 

 rows in the anterior region (more often 5 or 6), and 3-5 in the lat- 

 eral rows ; 3-6 in the middle region in both sets of rows : and 2-3 in 

 the posterior region. Aside from a decided bend at the proximal end 

 (PI. X, Fig. 30) each seta is straight. 



INTERNAL CHARACTERS 



Brain. — This organ (PI. X, Fig. 31) lies in I and II, chiefly in 

 the latter. The anterior margin is concave, while the posterior margin 

 is distinctly truncate. The lateral margins diverge caudad for about 

 two thirds of their length. Figure 31 shows the characteristic shape 

 of this organ. In transverse sections it is broadly elliptical in outline. 

 The entire organ is surrounded by a well-developed neurilemma which 

 is somewhat thickened between the roots of the commissural trunks. 

 Two sets of supporting strands attach the posterior region to the body 

 wall. 



Peptonephridia. — There is a pair of these organs ventrad to the 

 digestive tract, one on the right side and one on the left. Each opens 

 separately into the alimentary canal in a latero-ventral position in IV. 

 There is some variation as to the exact place of opening, some speci- 

 mens showing it near the middle of IV while in others it is in the pos- 

 terior part of IV. However, in all cases the opening occurs in IV. 

 These organs (PI. X, Fig. 34) are long and unbranched. They are 

 tubular, with but a single lumen, which is large in comparison to the 

 size of the organ. Immediately beyond the union with the digestive 

 tract each peptone])hridium turns abruptly caudad and extends parallel 

 to it. The length varies somewhat in the various specimens. In some 

 cases they extend into VI but in others only into V. Sometimes the 

 terminal parts extend around the alimentary canal and end dorsad to it. 

 One of the specimens examined, showed a peculiar condition in which 

 one of the organs, about midway of its length, gave rise to a single, 



