510 Mr. C. R. Narayana Rao 07i the Anatomy of 



in otlier earthworms it is almost a normal feature. In 

 discussing the phyletic relations of the different genera 

 of the family Moniligastridse, Dr. Michaelsen, who, in the 

 desciiptiou of the species D. ivillsi, known from the Central 

 Provinces, Deccan (Hyderabad), and W, Himalayas, records 

 *' Haufig rudimentare Prostateu im 9 Segment,^' remarks 

 " that this structure confirms the statement of Rosa 

 (adopted by myself) that the genus Drawida has arisen from 

 the holoandric genus Desmogaster by the loss of the first 

 pair of male organs, as well as a dislocation of all the 

 generative organs, with the exception of the spermatheca.^' 

 Dislocation of the generative organ there certainly has been 

 in D. somavarpatana, in so far as the anterior sperm-duct has 

 lost a separate exit (in the intersegmental groove 9/10), and 

 a portion of it lies in segment 10, where it opens into the 

 spermiducal gland, but the disappearance of one of the pairs 

 of male organs has not taken place. There can be no doubt 

 as to which pairs of seminal vesicles oi Desmogaster those of 

 Draivida correspond, and, in order to homologise them, it is 

 necessary to assume that in its evolution Draivida has arisen 

 by the suppression of somites 8 and 9 in the archaic ancestral 

 Desmogaster. In one individual of D. somavarpatana in my 

 collection I notice a partial suppression of segments, and in 

 the Oligochseta generally similar partial or total disappear- 

 ance of somites is not uncommon as individual variations. 

 Furthermore, the suppression of" somites must have pre- 

 ceded the disappearance of one pair of seminal vesicles in 

 the course of descent, as is evidenced by the anatomy of 

 sexual apparatus of both D. willsi and D. somavarpatana. 

 If the hypothesis of the suppression of somites 8 and 9 

 is correct, then the anterior pair of the spermatheca of 

 Desmogaster correspond with those of Draivida, the last hearts 

 (segment II) oi Desmogaster would in that case lie in segment 

 9 in Drawida. The seminal vesicles suspended from septa 

 10/11 and 11/12 in Desmogaster would be homologous with 

 those suspended by septum 9/10, and those lying in somite.s 11 

 in D. somavarpatana, and so with respect to the ovaries. 

 It is obvious that the holoandric sexual apparatus of 

 D. somavarpatana brings the genus Drawida nearer to 

 Desmogaster, besides pointing to a possible immediate 

 descent. 



Egg-sacs. — They are large, trilobed (being constricted 

 more or less by septa), yellow structures lying on the 

 oesophagus and gizzards, and are suspended from the pos- 

 terior face of septum 10/11. They extend as far behind 

 as segment 16. The ovaiics are greatly lobulated organs 



