SYSTEMATIC POSITION OF A GIGANTIC EAETHWOEM. 67 



in ein kleines, unter der Haul; liegendes Blaschen fiihren, es scheinen Schleimabson- 

 derung-swerkzeuge (oder Respirationsorgane 1) zu sein." From this description it is 

 clear that Rapp did recognize the peculiar form of these organs in Microchwta. On 

 ■ opening the body of the animal immediately after it had been killed by immersion in 

 weak spirit a number of long oval sacs, distended by their fluid contents, were apparent 

 in several of the anterior segments of the body, a pair to each segment ; it appeared at 

 first that these might be the copulatory pouches, since the rest of the organs— which lies 

 almost under the alimentary canal, and close to the mesenteries, which are here specially 

 thickened and muscular— was invisible • on further dissection, however, these vesicular 

 structures turned out to be diverticula of the duct of the nephridium. 



Several of these are displayed in PI. XV. fig. 6 ; each consists of (1) a tuft of coiled 

 glandular tubes communicating with (2) a wide, but thin-walled duct which narrows 

 abruptly into a short, thick tube, distinguished from the rest of the duct by its yellow 

 colour; this latter opens on to the exterior by a pore situated just behind the more 

 dorsally placed pair of setse. The duct of the nephridium, near the external opening, 

 gives off posteriorly a long, oval, csecal tube ; this is supported by a delicate membrane 

 which runs along the whole of its posterior surface, and is attached to the body-wall. 



The nephridia of the anterior part of the body, down to about the twenty-seventh 

 ring, have the same structure that has been described; there are a pair to each 

 segment as far forward as that which immediately follows the pharynx, which is 

 bounded in front by the most anterior of the specially thickened mesenteries. In 

 front of this mesentery there are only two pairs of nephridia, which are imbedded 

 among the confused mass of muscular fibres representing the most anterior mesenteries. 

 I am not able to state how many segments are included in this region of the body, 

 unless the seta? really mark the number of segments, in which case there are three. 



The internal opening of the segmental tubes, however, is not within the same 

 segment that contains the greater part of the organ, and on to the outer wall of which 

 it opens ; it was quite easy to make out that the proximal portion of the tube perfo- 

 rated the mesentery forming the anterior boundary of the segment, and terminated 

 freely within the cavity of the segment in front in a ciliated funnel (PI. XV. fig. 6) ; 

 about -± of an inch, or rather less, of the proximal clear-walled portion of the tube 

 depended freely within this segment. A similar arrangement is usual among Earth- 

 worms. In the hinder part of the body, from segment twenty-eight onwards, the 

 form of the segmental organs is a little different. The glandular portion consists, as 

 in the more anterior series, of a tuft of tubules generally disposed in loops, the tubes 

 forming the loop being variously coiled round each other. This part of the organ is 

 situated close to the ventral blood-vessel, and is partly covered by the alimentary canal, 

 as in the more anteriorly placed nephridia ; it appears, however, to be proportionally 

 smaller. The duct forms a wide, thin-walled tube, and opens by a thick, short, terminal 

 portion ; the duct is, however, prolonged beyond its aperture and towards the dorsal 



