OligocJiacta.] SUBANTARCTIC ISLANDS OF NEW ZEALAND. 269 



Rt'DiarJis. — In an important monograph of the earthworms of south-west 

 Australia, Miehaelsen* proposes to subdivide the older genus Notiodrilus into 

 two genera, one of which has a well-developed gizzard, and the other has it in 

 a vestigial condition. To the former he gives the name Eodrilus ; the latter 

 group of species he ])laces in the genus Microscolcr. for which he gives an amended 

 diagnosis. 



His diagnosis of Eodrilns oniv differs from that of Nofiodrilus'f in the words 

 " gizzard well developed." In it lie includes three New New Zealand sjjecies — E. 

 annectens, E. hnplocijstis, and E. paludosus. 



The amended genus Microscolex ( = Notiodrilus, Mich. -|- Microscolex, Rosa) con- 

 tains species in which there are two pairs of prostates, on segments 17 and 19, with 

 the male pore on the 18th (the characteristic old Acanthodrilijie condition), as well 

 as sjjecies with only one pair of prostates and male pores, both on the 19th segment 

 (the typical Microscolex condition). He separates the former from Eodrilus merely 

 on account of the minute gizzard. It seems to me that the double prostate pair is 

 a more important feature than the size of gizzard, which may, one would imagine, 

 readily be associated with the nature of the food. The only recommendation for the 

 union of the old genera Notiodrilus and Microscolex is that by the removal of those 

 species wdiich he includes in Eodrilus he obtains a group of species which has an 

 antarctic circumpolar distribution ; whereas Eodrilus is more diffusely distributed, 

 but at the same time contains several species found in the southernmost lands — 

 indeed, half the species are subantarctic. 



I regret that I cannot follow him in thus rearranging these sjjecies. It seems to 

 me that on grounds of convenience and evolution J the name Notiodrilus should be 

 retained for the w^orms with the two pairs of prostates, and that to make use of the 

 name Microscolex for the mixed set of species is undesirable, quite apart from the 

 insufficient gromids for such a grouping as he proposes. In this paper, therefore, 

 I shall retain the nam(^ Notiodrilus as defined by Michaelsen§ in 1899. 



I may point out that Miehaelsen does not seem quite consistent in the value he 

 puts upon this gizzard-character. He uses it also to distinguish the genus Perionyx 

 from Perionychella, the former having a vestigial gizzard, the latter a more or less well- 

 developed one. Yet in an account of some new species of these genera from India, 

 1907 (" Neue Oligochaten von Vorder-Indien," &c.), he describes species of both 

 in almost identical terms : thus, several species of Perionychella are stated to have 

 " very small gizzards, only a little thicker than the neighbouring part of the oeso- 

 phagus." For instance (p. 156), P. sikkimensis : " Ein kleiner cylindrischer Muskel- 

 magen in 6 (?) Segment, kaum dicker als die benachbarten Oesophaguspartien, aber 

 nicht eigentlich rudimentar." Of Perionyx himalayrmus he writes of the gizzard, 

 " l])erselbe ist kaum dicker als die benachbarten Partien des Oesophagus und hat 

 kaum dickere Wande." What remains of the distinction between the two genera ? 



* Miehaelsen, Die Faiuia S.W. Austral., bd. i, Oligochaeta, p. 138. 



t Miehaelsen, " Das Tierreieh : Oligochaeta," 1900, p. 128. 



J Aeeording to Miehaelsen^ species of Microscolex may arise at different times, in different parts 

 of the world, from different species of Notiodrilus. This thesis involves so profound a modification 

 in the accepted ideas of evohition that space will not permit me to discuss the problem here. 



§ Miehaelsen, Zool. Jahrl). Syst., .xii, 1899, p. 239. 



