ON INDIAN OLiaOCH^TA. 109 



7. Oontributions to the Morpholof^y, (Classification, imd 

 Zoogeogruphy of Indian Oligoclipeta. By J, Stephen- 

 son, M.B., D.Sc, F.Z.S., Lecturer in Zoology in the 

 University oF Edinburgh. 



[Received October 29, 1921 : Read February 7, 1922.] 

 ( Plate I . * Text-figures 1-19.) 



Contents. Page 



IV. On tbe dift'use production of Sexual Cells in a species of 



Chcetogaster (faui. Naidida;) 109 



V. On Drawida japonica (Mclilsn.), a Contribution to the 



Anatomy of the Moniligastridse 119 



VI. On the Relationships of the Genera of Moniligastridse ; 

 with some Considerations on the Origin of Terrestrial 

 Oligochseta 133 



IV. — On the diffuse production op Sexual Cells in a species 

 OF Gh.^togaster (fam. Naididje). 



The Naididee are a family of fresh- water Oligochseta, of small 

 size, in which the usual mode of reproduction is asexual, by 

 fission. Sexual reproduction probably occurs, at times, in all; 

 but in many, perhaps the majority, of species, and in some whole 

 genera, it has not as yet been observed. Where it has been 

 described (except in the genus Fristina, where the organs are two 

 segments further back) the testes and male funnels are in segment 

 V, the atria and male apertures, and also the ovaries, in segment 

 vi. Except in C/uetoc/asier, a single sperm-sac is constituted by 

 a posterior bulging of septum 5/6, and an ovisac, which envelopes 

 the sperm-sac, by a similar protrusion of 6/7 ; the sexual cells 

 given ofl' from the gonads enter the sacs, where they ripen, and 

 ultimately again leave the sacs to be discharged. 



Ghmtogaster is a somewhat aberrant genus of the Naididfe, 

 which was separated as a distinct family (Chaetogastridfe) by 

 Vejdovsky. It agrees, however, with the other genera of the 

 Naididfe in the prevalence of asexual multiplication, and (so far 

 as hitherto known) with the majority (all except Pristina) in the 

 position of the gonads in segments v and vi. Thus Vejdovsky 

 (6) figures and describes the testes and ovaries of C. diaphanus 

 in these segments; while Beddard (1) says that "the sperma- 

 thecpe, testes, &c., are in the same segments in both the ' families ' 

 Naidomorpha and Chfetogastridse." There appear to be no 

 detailed descriptions of the sexual organs in any species of later 

 date than these monographs, except my own of C. orientalis (4). 



The species of Chcetogaster which is commonest in Lahore in 

 N. India is that just mentioned, which I described first (3) as 

 C. pelhiciduSf but later (the specific name being preoccupied) 

 called orientalis (4). In this second paper I gave a description 



* For explanation of Plate I., see page 132, 



