216 MR. F. E. BEDDARD ON A [Mat. 20, 



is colourless asiu all the other species except jE. ehrenbergii, where, 

 according to Laukester ', it is of" a pinkish colour. 



There are a large riumher of pairs of nephridia present, while in 

 JE. variegatum there are onlj' three pairs, occupying sej^ments 4-6. 

 They are Tery readily visible, and the terminal aperture into the 

 ccelom is extremely obvious, lying midway hetvveen two successive 

 seta-bundles. The ccelomic aperture can hardly be termed a 

 " funnel," as it is only just perceptibly wider than tlie rest of the tube. 

 The external orifice of the nejihridium is placed close to the median 

 ventral line. Although the segmentation of ^olosoma does not 

 affect the ccelom, there being no mesenteries present, it is clear that 

 the position of the nephridia is such that, were mesenteries to make 

 their appearance, each nephridium would be entirely contained in a 

 single segment ; the external orifice is in fact in advance of the ccelo- 

 mic aperture (fig. I). This is of some little importance, inasmucli 

 as in Ctenodrilus '^, undoubtedly a near ally of ^ulosoma, the single 

 pair of nephridia are entirely contained within the first segment of 

 the body. Again, in Polyyordius ^ the funnels of the nephridia, 

 although they come into close contact with the septum which 

 divides the segment containing the nephridium from the one in 

 front, do not actually perforate it. Polijyordius is certainly a very 

 primitive Annelid ; and since the same conditions obtain in the 

 Capitellidse and other Chsetopods, there are some reasons for 

 believing that tlie restriction of a nephridium to a single segment is 

 primitive. On tlie other hand, it is almost universally the case 

 among the Oligochseta that the funnel lies in t'ne segment in front 

 of that which bears the external aperture of the nepiiridium. Again, 

 the nephridia of JEolosomu are, as has been pointed out by Vejdov- 

 sky, attached to the parietes by simple unicellular muscle-fibres. 

 This is perhaps to be looked upon as a primitive arrangement, since 

 the embryonic nephridium of AUolohophora is, according to 

 Lehmann, attached in a similar fashion \ The characters of the 

 funnel are important ; so far as I can ascertain from a single fortu- 

 nate section (fig. 4) it is composed of only two cells ; there are at 

 any rate only two nuclei present, and one of these is rather in 

 advance of the other. It is a fact which favours some views which 

 I have put forward elsewhere ^, as to the origin of the Annelid from 

 the Platyhelminth excretory system, that in this primitive segmented 

 worm the nephridial funnel should be, at most, two-celled. As to 

 the structure of the nephridia, they consist, as in all Oligochteta, of 

 " drain-pipe cells." 



The difference in the number of the nephridia between the indi- 

 viduals which I have examined and those which Yejdovsky has 



1 Linn. Trans, vol. xxvi. 1869. 



2 The most recent paper known to me on this worm is by Dr. Scharff. 

 Q. J. M. S. vol. xxvii. n. s. 



3 Fauna und Flora des Golfes von Neapel, xiv. Monograph of Polygordius, 

 by L. J. Fraipont. 



* Jen. Zeitscbr. 1888, pi. xx. fig. 7. 

 ' Q. J. Micr. Sci. 1888, pt. i. 



