248 Proceedings of the Royal Physical Society. 



even anterior region, of the olitellum, which is then ventrally 

 incomplete, as, e.g., in Trigaster Lankesteri. This arrange- 

 ment leads to the Geoscolecid^e and Lumbricidae. 



" The Moniligastridse can, I think, be regarded as modified 

 Geoscolecidse. The passage between the Geoscolecidse and 

 the Lumbricidae is effected by Criodrilus, in which the male 

 pores are immediately in front of the clitellum (Benham). 

 According to this way of looking at the matter, the least 

 modified forms of the Perichsetidae will be sougjht for in 

 Megascolex — that is to say, in those Perichaetidae in which 

 the clitellum is not limited to three segments, and in which 

 the setae still show median intervals. In these forms there 

 are no lateral intestinal coeca, and the nephridia have still 

 the normal form, as I have seen in Megascolex {Perichceta) 

 armatus, Beddard. 



" Now it is precisely in Megascolex (as thus defined) that 

 bundles of penial setae are still found, which are wanting in 

 other forms. These are found in M. arwMus, where they 

 exist in relation to the male pores, and \yl Megascolex {Perichceta) 

 ceylonicus, Beddard : the latter species would appear, accord- 

 ing to Beddard,^ to possess in front of the usual apertures, two 

 others which lead into a blind tube, which may be regarded 

 as a vestige of the first pair of male openings in the 

 Acanthodrilidae." 



There is an obvious discrepancy here with views expressed 

 on an earlier page. If it be admitted that one of the reasons 

 for regarding th^ Acanthodrilidae as the primitive group is the 

 presence of numerous nephridia per somite in A. multiporus, 

 it can hardly be said that Megascolex (as defined by Eosa) comes 

 nearest to the primitive form because it has normal nephridia 

 — that is, one pair per somite ! Apparently, however, Dr Eosa 

 was of opinion that the minute nephridia of Periclueta (s. str.) 

 were in a degenerate condition, though he quoted (p. 19) 

 Benham's paper, " Studies on Earthworms, pt. i. — Q. J. M. S., 

 vol. xxvi.," in which work Benham refers (at p. 256) to his 

 own and my observations upon Perichceta. 



1 Notes on some Earthworms from Ceylon and the Philippine Islands, 

 including a descrii)tion of two new species — Ann. and Mag. Nat. Hist., 

 ser. 5, vol. 17 (1886), p. 89. 



