AQUATIC OLIGOCHAETA OF THE INLE LAKE. 



By J. Stephenson, D.Sc, Lt.-Col, I.M.S., Professor of Zoology, 

 Government College, Lahore. 



Of the small but interesting collection of Oligochaeta made by Dr. 

 Annandale at the Inle Lake in the Southern Shan States, and kindly- 

 handed over by him to me for examination, the most remarkable speci- 

 mens are a series of Branchiura sowerhyi. These have enabled me to 

 demonstrate the existence of a penis (perhaps a pseudopenis, according 

 to Michaelsen's definition, 5), and to show that in this form also, as well 

 as in Kawamuria japonica (11), the muscular coelomic chamber is the 

 apparatus for its extrusion. The amount of variation shown by these 

 specimens in such features as length of body and length and number of 

 gills is surprising. 



I have taken this opportunity of also referring to two varieties of 

 Nais communis from the Punjab which have recently come into my 

 hands, though these are not part of the Inle collection. 



Family NAIDIDAE. 



Genus CHAETOGASTER. 



Chaetogastei annandalei, Stephenson. 



Inle Lake, S. Shan States. In Sponge (Ephydatia fluviatilis) ; 28tli February, 

 1917. N. Annandale. Several specimens, none sexually mature. (No. W. 

 113-1.) 



The identification rests on a comparison with individuals of the original 

 batch of sj)ecimens from L. Biwa in Japan (11). The present specimens 

 are about one-fourth larger ; in length a chain of two individuals is 

 •89 mm., the first being -63 and the posterior -26 mm. ; the diameter is 

 •175 mm. ; the setae of segment ii are 90jU, and of more posterior seg- 

 ments 60/x in length. 



Chaetogaster limnaei ? V. Baer. 



In same tube as the above ; several specimens, none sexuallv mature. (No. W. 

 135-1.) 



The length of these specimens is no greater, in the preserved condi- 

 tion, than that of C. annandalei, with which they occur ; but the other 

 proportions are quite different ; — they are about twice as thick, and the 

 setae also are markedly larger. So far as I can see, the only distinction 

 between these specimens and C. limnaei is the rather smaller number of 

 setae in these, — 6 or 7 in segment ii and 3, 4, or 5 behind. C. limnaei 

 has up to 8 — 12, according to Vejdovsky (12), who also remarks that the 

 hinder segments have commonly more than the anterior ; this is not the 

 case here, but it is pretty certain that the above numbers do not repre- 

 sent the actual state in the living animal, and that a number of setae 



