V I I .— D ESCRIPTION OF AN OLIGOCH^TE 

 WORM ALLIED TO CH^TOGASTER. 



By J. Stephenson, Major, I. M.S., Professor of Biology, 



Government College, Lahore. 



The worm described below was found in water taken from a 

 tank in the pleasure-gardens at Shalimar, near Lahore, in the 

 early part of February, 1907. It lives well in water kept in small 

 vessels with a little green alga in the laboratory, and appears to 

 propagate itself asexually with freedom. Specimens have been 

 under observation at various times during the last month. 



External characters. — In length the animal measures from 

 I to 2 mm. ; the variations are considerable, and depend principally 

 on the stage which the asexual reproductive process has reached 

 {v. inf.). There is a short blunt prostomium, followed by a region 

 slightly swollen in an ovoid manner and corresponding to the 

 pharynx ; the rest of the body is of uniform diameter, showing a 

 wrinkling corresponding to the degree of contraction of the animal, 

 but no regular annulation. The anterior end of the body is studded 

 with a few fine hairs ; and similar hairs also occur posteriorly in 

 the neighbourhood of the anus. The whole animal is very trans- 

 parent. 



Segmentation. — As just said, there is no external annulation ; 

 the segmentation is, however, indicated externally to some extent 

 by the bundles of setae. The first setae are placed ventro-laterally 

 on the slightly swollen anterior region, and may be taken to belong 

 to the second body-segment ; the next bundles are placed some 

 distance further back, this achaetous interval being in length equal 

 to about three of the immediately following segments. The bundles 

 then succeed each other regularly, being placed, however, closer to- 

 gether at the posterior end of the animal. 



Internally the segmentation is defined by the septa, of which 

 the first occurs at the posterior end of the pharynx, behind the level 

 of the first bundle of setse, and may be taken to be the posterior limit 

 of the second segment : the next septum occurs at the posterior end 

 of the oesophagus, similarly delimiting the third segment ; in the 

 region of the crop there are three septa, the first of these about the 

 junction of the anterior and middle, the second about the junction of 

 the middle and posterior thirds, and the last near the hinder end of 

 the crop. The second bundle of setae occurs at the level of the 

 posterior part of the crop, in the sixth body-segment according to 

 the limits established by the septa. Segmentation is also evident 

 internally in connection with the ganglia of the ventral nerve-cord 

 and with the nephridia (v. inf.). 



