igo8.] W. MiCHAEi,SEN : Oligochceta of the Indian Empire and Ceylon. 201 



a tuft-like bunch). But these technical difficulties should not cause us to undervalue 

 the systematic importance of the nephridial characters. 



The underestimation of these nephridial characters has misguided BENHAM in 

 other ways. Firstly, he places near the micronephric Octochsetine genus Dinodrilus , 

 the meganephric genus Dinodriloides} As I have pointed out on another occasion, 2 

 Dinodriloides is not at all allied to Dinodrilus. It is a genus of the sub-family Acan- 

 thodrilinœ , nearly allied to Rhododrilus as lately defined by me {I.e., p. 142). It re- 

 sembles Dinodrilus and differs from Rhododrilus only in the increased number of 

 setae in one segment, and this increase is an occurrence of only secondary systema- 

 tic importance, noted in different sub-families of the M egascolecidce and even in other 

 families of earthworms (genus Periscolex of fam. Glossoscolecidœ). Still more con- 

 fusion has been caused by BENHAM in the well-defined sub-families Octochœtinœ and 

 AcanthodrilincB , when he put some Octochsetine species into the acanthodriline genus 

 Plagiochceta:' The type species of Plagiochceta, P. sylvestris (HUTTON) (=P. punc- 

 tata, BENHAM), belongs to the sub-fam. AcanthodrilincB, to a group of nearly allied 

 genera characterised by the position of the nephridial pores alternating in two dif" 

 ferent lines at each side of the body (genera Maoridrihis, Neodrilus and Plagiochœta). 

 This character may a priori seem to be of little systematic importance. But the 

 geographical restriction of the group in which it is found is remarkable. It is a 

 character that occurs only in a small group of holoandric * A canthodrilince with free 

 testes and sperm-duct-funnels, which is divided into three genera only by the ordinar^^ 

 principles of the microscolecine decrease {Neodrilus from the acanthodriline genus 

 Maoridrilus) and the perichaetine increase of setae {Plagiochœta from the lumbricine 

 genus Maoridrilus) . All the species which bear this character — the number of them is 

 rather great — are endemic in the New Zealand region. This character is found in none of 

 the many extra-New-Zealand AcanthodrilincB. We may therefore conclude, as regards 



' W. B. BENHAM, On some Edible, etc., I.e., p. 226. 



2 W. MICHAELSEN, Oligochaeta; in Die Fauna Südwest- Australiens, etc., bd. i, p. 140. 



2 W. B. BENHAM, On the Old and some New Species of Earthworms belonging to the Genus Plagio- 

 chaeta; in Trans. New Zealand Inst., vol. xxxv, art. 31. 



* BENHAM says about Neodrilus, which belongs to this group, ' but in Neodrihis, which 



MICHAELSEN has termed a "microscolecine form," the number of testes h^ also been reduced' (On 

 some Edible, etc., I.e. p. 229). Is this not a mistake ? Unfortunately I have not at hand BEDDARD's 

 original description of N. monocystis, but I believe that my note, ' 2 Paar freie Hoden und Samen- 

 trichter' (Oligochaeta; in Tierreich, Lief. 10, p. 125), according to which Neodrilus would be holoandric, 

 is taken from the original description. Furthermore BENHAM's note, according to which Neodrilus would 

 be meroandric, does not conform with his earlier notes. In " Notes on two Acanthodriloid Earthworms 

 from New Zealand " (in Quart. Journ. Micr. Sei., N.S., vol. xxxiii, p. 292 , he says, ' The testes and ovaries 

 have the usual position '—that is, for the definition of an "Acanthodriloid earthworm" of that day, 

 a holoandric arrangement. The holoandric nature of A^^. monocystis may also doubtless be derived from 

 BENHAM's delineation {I.e., pi. xv, fig. 8). Here he figures in a diagrammatic longitudinal section 

 through the body-wall 'two' sperm-ducts, spoken of in the explanation of plates {I.e., p. 310) as 

 ' sperm-ducts,' i.e., in the plural. A^. monocystis having, then, two sperm-ducts at each side, must have 

 as well two sperm-duct-funnels at each side and must be regarded as " holoandric " in conformity with 

 these earlier notes of BENHAM. 



