iQoy] Records of the Indian Museum. 237 



(2) ClL^TOGASTER PELLUCIDUS, n. Sp. 



The following interesting form was obtained in the tank in the 

 pleasure-gardens atShalimar, and was also found in fair numbers in 

 the duck-pond in the Lahore Zoological Gardens. Specimens were 

 under observation in the laboratory'' at various times during April 1907. 



External characters. — The worm is much larger and thicker 

 than C. punjabensis, recently described from Shalimar. The 

 ordinary length is about 5 mm., but some of the longer chains, 

 especiall}^ when extended, ma}^ reach 10 mm. Its general shape 

 will be immediately understood by a reference to the figures in 

 plates ix and x ; fig. i, however, was drawn from a somewhat con- 

 tracted specimen, and the usual shape is more accurately expressed 

 by some of the other drawings. The animal is very transparent. 



It seems unnecessary to describe a prostomium, the mouth 

 being large, obliquely placed ventro-anteriorly, and reaching to 

 the anterior extremity of the animal. The pharyngeal region is 

 beset externally with a large number of minute irregularities, pro- 

 bably small chitinoid, or at least cuticular, elevations {v. fig, i), 

 mostly elongated in an antero-posterior direction ; their shape and 

 disposition are represented in text-fig. 2. The anus is terminal. The 

 animal is very contractile, and may, in this condition, appear to 

 be little more than half its normal length, and double its normal 

 thickness. It moves largely by means of these contractions and 

 extensions of the body assisted by its setse ; in backward progression 

 the hinder end of the body may be first over-extended, then sharply 

 flexed ; the setse, with their points directed forwards, are thus 

 brought to impinge forcibly on an}^ subjacent object, which serves as 

 a point of resistance as the animal thus jerks itself backwards. In 

 anterior progression the points of the setse are directed backwards. 



Segmentation. — The rudimentary nature of the prostomium 

 has been mentioned ; neither it nor any of the succeeding segments 

 are marked off by any external annulation, and other means of 

 delimiting the segments also fail us in the anterior part of the 

 body. As elsewhere, the first group of setse may be supposed to 

 mark the second segment ; but posterior to this there is a region 

 of the body which is entirely achsetous, which possesses no nephridia, 

 where the ventral nerve cord is not marked by distinct ganglia, 

 and where the septa also are irregular or wanting. There can, 

 however, be little doubt that the second group of setae belongs to 

 the sixth segment, since this is the rule in the genus Chcetogaster , 

 to which in other respects the present form shows a close corres- 

 pondence. In C. punjabensis, for example, the segments can be 

 counted by means of the septa ; and there can be no doubt of 

 the close relation between that species and the present form. The 

 body is continued posteriorly to a variable length, the segments 

 being marked throughout this extent by definite septa, by the 

 setal bundles and by nerve ganglia. The shortest animal I have 

 met with (text-fig. 2) showed in all eleven segments, and this may 

 be taken as the normal length of a single individual. 



