4 86 



Memoirs of the Indian Museum. 



[Voi.. V, 



relation varies, so that in some cases the outer prong is only two-thirds as thick as 

 the inner, while towards the posterior end it may be only half as stout. 



The single-pointed needles (fig. ib) are about yofx or a 

 little more in length, and 3/* in thickness. They have 

 the usual double curve, the distal curve however being 

 more marked than the proximal. They end in a single 

 sharp point; and the nodulus is slightly distal to the 

 middle of the shaft. 



A certain number of double-pointed setae are found 

 in which the outer prong is small. Thus they present 

 an intermediate character ; and the single-pointed setae 

 may be conceived as originating from the double-pointed 

 by the diminution and ultimate loss of the outer prong. 

 The ventral setae begin in segment ii, and are absent 

 in xi. They are usually three per bundle throughout 

 Fig. z.—Monopylephorus parvus, the body, including the hinder end, but in the anterior 

 rt . . . , ,'. - , ' . segments four and five are met with. The bundles are 



a. Double-pointed seta from an anterior 

 dorsal bundle, x 760 



b. Single-pointed seta from a ventral 

 bundle behind the middle, x 760. 



composed of only double-pointed setae throughout the 

 anterior half of the body ; single-pointed setae are found 

 behindthe middle, and at first only occasionally ; they are 

 commoner at the hinder end, but even there are outnumbered by the double-pointed. 

 The dorsal setae begin in segment ii ; the number per bundle is here also three, 

 four, or five; — three in one or two of the most anterior segments, then four or five as 

 far as the clitellum, and thenceforward three or four,— more usually three, at any 

 rate in the hinder part of the body. In the most anterior segments only double- 

 pointed setae are found ; these soon begin to be replaced by the single-pointed, and 

 the change is completed shortly behind the clitellum, or, in another specimen, by 

 about the middle of the body. The dorsal thus differ from the ventral bundles in the 

 much greater proportion of the single-pointed setae. 



The alimentary tube is but little differentiated into distinct regions. Chlorago- 

 gen cells begin in segment vi, and thereafter the characters of the canal remain much 

 the same throughout the body. The pharynx is remarkable for the height of the 

 epithelium on the roof; an area of columnar cells, -with an abrupt margin, forms a 

 plate-like or sucker-like projection into the cavity, and exactly resembles the struc- 

 ture called the (l pharynx" in the Bnchytraeidae. The " pharyngeal gland cells" 

 are arranged in four cords which are applied dorsally and dorso-laterally to the 

 pharynx, as described and figured for M. limosus by Nomura (y). Numerous similar 

 cells are found on the body -wall, where they form considerable masses at the level of 

 the hinder part of these cords, as well as for some distance behind this, as far as seg- 

 ment vi; a number are also seen on each side of the ventral nerve cord in the oeso- 

 phageal region. 



The body-cavity corpuscles have the characters described by Moore (6); a fairly 

 large one is io/x in diameter. 



