2o6 Records of the Indian Museum. [Vol. VI, 



Chaetogaster known (Annandale gives the length of an individual 

 which is not budding as about i mm.). 



The margin of the mouth does not reach quite to the anterior 

 tip of the body ; there is hence a small prostomium. The mouth 

 IS large, and leads directly into the pharynx, as in other species. 



The setae (fig. i) are slender, with a slight i -shaped curve, 



double-pronged ; the distal prong is half as long again as the proxi- 

 mal, but only two-thirds as thick at its base ; the nodulus is 

 proximal to the middle of the shaft, the proportions being : — 

 proximal to nodulus : distal to nodulus : : 2 : 3. There is no 

 difference in type between the setae of the most anterior bundles 

 and those situated more posteriorly, but there is a considerable 

 difference in length ; those of segment ii average about "og mm., 

 those of the other segments about "06, or two-thirds the former. 

 There are on the average four setae per bimdle. 



In the specimens which I received, A possessed eight fully 

 formed segments, and B three or four; between the two was 

 a budding zone, in which young setal bundles — the anterior 

 destined to belong to the posterior end of A, the posterior to 

 the anterior end of B after separation — were occasionally seen. 



Fig. I. — Chaetogaster spoMg-^Mae : seta belonging to segment ii ; x 890. 



The animals therefore begin to divide when they possess eleven 

 or twelve segments : the budding zone forms posterior to viii 

 i^n == 8), and in the budding zone presumably eight or nine new 

 segments are formed, — three or four to complete A, and five 

 to form the anterior end of B (of these five only the second bears 

 setae) ; the ninth segment of the original undivided animal 

 ultimately becomes the sixth of B. 



Annandale mentions " longitudinal rows of minute, irregular 

 tubercles on the 'head'." I have described similar elevations 

 in C. orientalis (== C. pellucidus; Rec. Ind. Mus., vol. i, part 

 3, and cf. pi. ix, fig. i). I have however more recently convinced 

 myself that these appearances are due merely to the muscular 

 fibres which pass between the pharynx and the body- wall, and 

 represent in fact the outer ends of these fibres ; the same may 

 not improbably be the case in C. spongillae. 



The pharynx is a simple wide tube ; it is followed by a 

 very short oesophagus, to which succeeds the dilated part of 

 the alimentary tract that I have previoush^ {loc. cit.) called the 

 crop ; a slight constriction separates this from another dilatation, 

 the stomach, which is followed by the intestine. Of these sections 

 of the tract, the pharynx occupies segments i — iii, as far as 

 the first dissepiment (f , v. inf.) ; the oesophagus is restricted 



