Benham axd Cameron. — yepliridid of Perieodiiln.s 191 



Art. XX. — Tlie Nephridia of Perieodrilus ricardi aiul of P. inont;inus. 

 By W. B. Benham, F.K.S., and Gladys Cameron, M.8c. 



[Rrdd bcjore thr Ofdi/o In.sfifitfe, 5th Xovej/iber, 1912.} 



The geiiuti Flagiochaeta was estaljlished 1)V Benliam in 1892 for a specie.s 

 which was termed P. 'punctata, and a full account of its anatomy will he found 

 in the journal cited (2). In this article a brief account of the nephridium 

 was given. The worm is meganephric, with alternating nephridiopores, but 

 differs from Maon'drilus in the perichaetinc multiplication of the chaetae. 

 It was, however, found later that the worm to which Captain Hutton had 

 given the naine Megascolex sylvestris belongs to this same specits. In 

 1902, Benham (3) described four new species which he attributed to Phiqio- 

 chaeta, and gave a history of the matter, with references to previous literature. 



Of these four species, P. Jateralis is meganephric, but has the pores in 

 a single series, as in Eodrilus of Michaelsen. P. rossi was described as micro- 

 nephric, as also were P. ricardi and P. montana ; but in the case of the 

 last two Benham, in a footnote to a paper (4) on " Some Edible and other 

 Worms " (1904, ]i. 229), stated that a re-examination of these had shown 

 him to have been in error ; they are really meganephric, though the organ 

 is small in comparison with the size of the worm, and is thrown into a 

 series of coils which simulates the scattered individual nephridia of a niicro- 

 nephric worm. 



Dr. Michaelsen (9), who has discussed so fully the systematic position of 

 the New Zealand worms, suggested in 1907 (p. 140), by his tabular arrange- 

 ment of the " holoandric Acanthodriline " genera, that the meganephric 

 P. lateralis should be placed in a new genus, on the ground that the nephri- 

 diopores are in line, instead of being alternate as in P. sylvestris. 



In 1909, in his memoir on the earthworms of India and neighbouring 

 lands, he again discussed (10, ]). 202) the systematic position of these four 

 worms, and suggested that the three " micron ephric " species shoidd be re- 

 moved from the genus Phif/ioc/Kiefa and placed in his genus Hoplochaetella : 

 and finally, in 1910, after examining material which Benham had sent him. 

 he recognized the distinctness of lateralis by erecting the genus Perieodrilus 

 for it (11, p. 61). As a result of this examination he confirms Benham's 

 statements for lateralis and rossi. In the case of montanus he was unable. 

 owing to the poor state of the specimen, to satisfy himself as to the true 

 condition of affairs, but was inclined to believe that it is micronephric. 

 As will be seen below, in this he was misled by the difficulty of tracing 

 out the tubules, owing to the presence, as he says, of the numerous cj^sts 

 of Gregai'ines. 



As to P. ricardi, he had no specimens at his disposal, and accepts 

 Benham's statements as to its being meganephric, and therefore ])laces it 

 in the genus Perieodrilus along with P. lateralis. During the expedition to 

 the subantarctic islands Benham obtained and described (1909, p. 275) 

 a new species, which he places in the genus Plagiochaeta ; but according to 

 Michaelsen's definition it should be called Perieodrilus plunketi. At the 

 same time, apart from the condition of the nephridia, it may be noted that 

 it differs from the other species in having a mere vestige of a gizzard, whereas 

 in P. latercdis this organ is well developed. As he has separated Eodrilus 

 from Microscolex {Notiodrilus) owing to the conditioi\ of the gizzard, ]>erhaps 

 this worm ought to be placed in a new genus ; but foi' the present it may be 

 left in Perieodrilus, as it is possible that the state of the gizzai'd may bt* 

 due to its mode of life — that is, it may be adaptive. 



