ANB ZOOGEOGRAPHY OF INDIAN OLIGOCH^TA. 



137 



ai-e apposed in copulation); otherwise the figures are identical 

 (text-fig. 12):— 



Text-fis-ure 12. 



h 



Eupolygaster. 



In Drawida and MoniUgaster the figure is as below (text- 

 fig. 13). 



Text-figure 13. 



JDraioida and MoniUgaster. 



The ovarian jjhamber corresponds to the ovarian segment in 

 the other genera; as in Eupolygaster, there is a single pair 

 of spermathecae and a single set of male organs. But there is 

 a further reduction still— another segment has disappeared. 

 Assuming for the moment that the similarly lettered segments 

 in text-figs. 11 and 13 correspond, c with c and g with gr, it will 

 be seen that the single testis sac of Drawida is left to correspond 

 with the two testis sacs and the intervening segment e of Desmo- 

 gaster ; in other words, there has been a squeezing together of 

 the segments, and the two testis sacs have fused. This fusion 

 probably gave at first a single sac with a vertical diaphragm ; 

 later the diaphragm disappeared (c/. text-fig. 14, c). In thus 

 fusing, the testis sacs have annihilated the space e — in other 

 words, the cavity of the segment between them ; the most 

 posterior heart, which was in this space, has also disappeared, 

 and hence in these two genera, Drawida and MoniUgaster, the 

 last heart is in the segment in front of the testis sac. The 

 actually existing testis, funnel and duct of these genera may not 

 improbably be the testis of the original anterior sac and the 

 funnel and duct of the posterior. 



Michaelsen (12) imagines the genns Drawida to have arisen in 

 a rather diflerent way—by the disappearance of the anterior set 



