AND ZOOGEOGRAPHY OF INDIAN OLIGOCHiETA. 141 



the letters show the morphological correspondences, and the 

 romau numerals show the actual segments (revised as above in 

 the case of Desmor/aster). 



(5) The Relationship of Moniligaster to Drawida. 



The genera Drcmida and Monilirjaster differ only in the fact 

 that Moniligaster has, and Drawida ha,s not, connected with the 

 ectal end of the spermathecal duct, a bilobed glandular appendage, 

 of which each lobe consists of a number of closely-packed branches. 

 In Drawida there may be a swelling on the end of the duct, or at 

 most a relatively small sac-like atrial diverticulum. 



Michaelsen (13) takes Drannda for the ancestor, Moniligaster 

 for the descendant ; he traces the history of the at first simple 

 duct in Drawida. In some species it " widens and is transformed 

 into a muscular coat. In other species of this genus this widened 

 muscular distal {i. e., ectal) end grows into a real muscular atrial 

 chamber, which further on enlarges at one side to form a 

 separate blind sac, depending into the second segment, or, m the 

 species D. robiosia and its subspecies, at two sides, forming two 

 outt^rowths, one depending into the seventh segment, the other 

 into the eighth, the two outgrowths being separated by the 

 septum 7/8,''- and the duct of the pouch entering the atrial 

 chamber at the angle between these two outgrowths. The 

 structure found in the species of Moniligaster may be compared 

 with this structure in D. rohusta. The two outgrowths of the 

 atrial cavity in the latter species are continued m Mondigaster 

 each into a large gland, consisting of a large, much-branched 

 tube, the branches and twigs of which are packed together and 

 enveloped in a peritoneal membrane." ^ .. ^ , 



This derivation does not seem easy to me ; I should preter to 

 read the series (if indeed it is a series) in the reverse direction. 

 I cannot see in Moniligaster any atrial chamber at all— only two 

 olands, with ducts which unite, like the limbs of a Y, to form a 

 single canal. This is well shown in Perrier's original plate (18) ; 

 my' own description of the condition in Perrier's species is 

 similar (22):— "The stalk (atrium) is relatively narrow, and 

 bifurcates, one branch going to each half of the mass. Neither 

 ■ the stalk' nor its two branches are in any sense sacs ; the 

 appearance is that of two ducts proceeding one from each halt ot 

 the mamillated glandular mass, which unite to form a common 

 duct; this common duct is less than half as long as the glandular 

 part and nowhere dilated." It seems difficult to imagine a 

 slight swelling of the end of the duct dilating, becoming a sac- 

 bifurcating, and then sprouting glands from each horn, itselt 

 concomitantly narrowing to a Y-shaped duct. If- the series 

 really is a natural one, it would be easier to read it the other way— 

 as a o-vadual reduction, of the glands to a non-functional vestige 

 and their final disappearance. It is possible that the glands are 

 entirely independent of the spermathecfe in origin ; compare 



