230 Dr. F. E. Beddard on the Genus Trichodrilus. 



The nephridia of Trichodrilus allobrogum are described by 

 (Jlaparele; but my own observations upon this British 

 species do not agree in many particulars with his. I rely 

 entirely, as to this part of the anatomy of the worm, upon 

 longitudinal sections ; I was unable to make any trustworthy 

 observations upon the living worm by reason of its opacity. 



Claparede remarks — and I am in agreement with him — 

 that the nephridia are absent in the first six segments of the 

 worm. He found these organs in the Vllth and VTIIth seg- 

 ments, but asserted their absence thereafter until the xinth, 

 where they again begin, and continue in following segments. 

 There is, I think, no doubt about the fact that, as in Phreato- 

 thrLv, according to both Vejdovsky * and myself f, the pairs 

 of nephridia are not necessarily limited to one segment. In 

 the present species the first pair lie in VII., but extend also 

 through VIII., IX., and a part of segment X. This was very 

 plain in my sections, and the continuance of the tube through 

 the septa quite clearly to be made out. I did not see the 

 funnel, which no doubt lies in segment VI., but I found the 

 duct leading to the external pore upon segment VII. In 

 segment XI. I could find no nephridia at all ; but in segment 

 XII. and the following these organs were again present. I 

 am not certain whether the difference between the species 

 described by myself here and that of Claparede, as is to be 

 inferred from his descripion, is a real one; for recently 

 Bretcher, in an account of Bichceta $anyuinea%, which species 

 Piguet considers to be referable to the genus Trichodrilus §, 

 has mentioned that the nephridium of segment vil. traverses 

 also segment VIII. Nor can it be considered that the exten- 

 sion of this nephridium settles the identity of the genera 

 Trichodrilus and Phreatothrix (which Michaelsen would join) 

 on account of the conditions observable in other genera of 

 the family. 



In Stylodriliis vejdovslcyi Benham || describes the first pair 

 of nephridia as extending through segments VII.— X. in pre- 

 cisely the same way as has been referred to above. 



In Lumbricidus variegatus Mrazek % found that a single 



* System, u. Morph. d. Oligocli. Taf. xi. fig. 18. 



t Proc. Zool. Soc. torn. cit. 



\ "Sud-schweitzerische Oligochaeten," Rev. Suisse Zool. viii. 1900, 

 p. 444. 



§ " Notes sur les Oligochetes," Rev. Suisse Zool. xxi. 1913, p. 141. 



|| " Notes on some Aquatic Oligochaeta," Quart. J. Micr. Sci. (n. s.) 

 xxxiii. p. 211. 



*\ " Beitrage zur Naturgeschichte von Lumbricuhis" SB. k. B6hm. 

 Ges. 1913. 



