igoS.] J. Stephenson : The Anatomy of some Aquatic Oligochceta. 269 



nephridia begin in the ninth segment and not the tenth, and that there are six pairs 



of oesophageal commissures, not five, the last being in the seventh segment, not 



the eighth. 



Pristina œquiseia, Bourne. 



This worm is also common in certain situations in or near Lahore; a large 

 number were obtainable at one time from a small tank surrounding an artificial 

 fountain in the Municipal Gardens. In general it closely resembles the former 

 species, and the description may therefore be considerably abbreviated. 



It is smaller than P. longiseta, averaging about 2 mm. in length; it resembles 

 the former species in the elongated prostomium, and frequent backward progres- 

 sion. 



The ventral setce are usually three in number in each bundle; in their characters 

 they correspond to those of P. longiseta. The dorsal setœ of the third segment are 

 not elongated. There are throughout the extent of the animal almost always two 

 in each bundle, of which one is capilliform, and in length equal to the diameter of 

 the body; the other a short '' needle " hardly projecting at all from the surface of 

 the body, straight and without nodulus; this second, short seta does not appear 

 to be an im.raature hair-seta, since its length does not vary, and in all the bundles it 

 is found, as said, just protruding from the surface. I have no record of a '' toothed" 

 condition of these setae similar to that of P. longiseta, but quite possibly I have 

 overlooked it. 



The alimentary canal may be described in the same words as that of P. longiseta. 

 Septal glands were seen in segments iv, v, and vi. 



The circulatory system is also on the same lines, and the oesophageal commissures 

 occur in exactly the same positions; only those in segments vi and vii were, however, 

 seen to be contractile. The corpuscles of the body-cavity are of the type described for 

 the former species; and the nephridia begin, similarly, in the ninth segment. 



Asexual reproduction was observed, and the number of segments appears to be 

 about 20. 



I have no record of genital organs in an undoubted specimen of this species ; the 

 appearances noted in an animal which most probably belongs to it are recorded 

 below. 



This species is distinguished from the last by the absence of the greatly elongated 

 setae of the third segment ; but it is evident that where the long setae have been 

 damaged, or broken off, or have fallen out altogether, the distinction will be difficult. 

 I have, I believe, been careful to take only specimens where these setae were quite 

 sound and uninjured for the purpose of the above description; and I believe, further, 

 that the distinction between the two forms can be made by the usually smaller 

 size of this second form, as well as by the peculiarities noted as common to all 

 the bundles of its dorsal setae, the general occurrence, that is, of only one long 

 capilliform seta with one short needle-shaped seta in each bundle ; my specimens 

 of P. longiseta have possessed varying numbers of setae of varying lengths in each 

 bundle, and all capilliform. 



