182 



Transactions. 



?ph./ 



wards, thrust the nephridia oat of their normal transverse position ; tlie 

 bladders are considerably extended, the poi'es terminal, and the outlet-canal 



opens at the opposite end. so 

 that there is no caecum. The 

 nephrostomial duct is particu- 

 larly long. 



In the 2nd segment of the 

 body lies the first nephridium, 

 in which the arrangement of 

 the folds is lost, and the result 

 is a compact mass of tubules, 

 coiled in a complicated manner, 

 and bound together by con- 

 nective tissue to the ventral 

 Surface of the body-wall. This 

 nephridial mass is subspherical. 

 ^ and of quite a noticeable size, 

 communicating with a large 

 bladder which lies lougitu- 

 VI dinally in the segment : this 

 can be traced quite easily to 

 nepJu'' |]-^g anterior end of the seg- 

 ment, and is seen to 2>enetrate 

 the body-wall to open to the 

 exterior by a pore on the 

 dorsal surface of the 2nd seg- 

 ment. This first nephridium 

 appears from the position of its 

 pore as well as from the modi- 

 fication, though slight, to act 



Fit 



Dissection of the first six segments of M. rosae 

 to show the nephridia : drawn nnder a dis- 

 .secting microscope. 



as a " pepto-nephridium "' (Benham) — i.e., its secretion is made use of in the 

 process of digestion of food. 



Course of the Nephridial Tube (fig. 8). 



The whole nephridium consists, as usual, of the winding of one lojig 

 excretory tube through the various folds. This tube is embedded in con- 

 nective tissue. The post-septal region is composed of the same four regions 

 as are found in Lnmbricus — viz., (a) long narrow tube, (b) short ciliated 

 middle tube or "' bridge," (c) long wide tube, (d) muscular duct or bladder 

 opening by the nephridiopore to the exterior. These dift'erent regions of 

 the excretory organ are best seen in fresh specimens, and do not show well 

 in preserved worms, though the windings may be traced out in unstained 

 nephridia, in which, too, the extent of ciliation is seen, while specimens 

 stained in picro-carmine or picric acid and afterwards mounted in glycerine 

 show well the dift'erent parts of the tube. I found that this method of 

 preparation gave better results than with borax or alum carmine for a stain 

 and a Canada-balsam mount. 



The course of the excretory tubule may be seen in fig. 8. The lung 

 narrow tube (a) commences at the proximal end of the funnel in the pre- 

 ceding Segment as the nephrostomial duct {n.d), which passes through the 

 .Septum, and enters the anterior fold as the outer narrow canal (a.o). 'Jliis 



