The Classification and Distribution of Earthworms. 247 



The first f^roup (that of tlie Eudrilidse and Perichietidce) are 

 affined by the possession of a complete clitellum^ of a com- 

 paratively constant position ; the male apertures are either 

 on the 17th or 18th sei^ment, on the hinder part of the 

 clitellum, or upon one of the immediately succeeding seg- 

 ments; the presence of prostates ;2 the presumed absence 

 of typhlosole. The last statement is the only one with 

 which I wish to find fault as being inaccurate, though I 

 desire to point out that Dr Eosa could not be aware of its 

 inaccuracy. As a matter of fact I have found a typhlosole 

 in some species of Ferichmta ; for example, in P. indica and 

 P. affinis.^ It is true that in these species the typhlosole is 

 small ; but it is not less developed than in such Acantho- 

 drili as A. Nova Zelandim. 



The second group (including the LumbricidaB, Geoscole- 

 cidffi, and ? Moniligastrida^) presents the following char- 

 acters: — A saddle-shaped (incomplete) clitellum, of very 

 variable position and extent ; male apertures inconstant in 

 position but always in front of the clitellum, or on the 

 anterior region of the clitellum ; no prostates ; very general 

 presence of a typhlosole, and (I suppose I may add) absence 

 of penial setae ; presence of only 8 setae iu each segment. 



These groups are indeed, as Eosa admits, rather different. 

 The Acanthodrili, he thinks, serve to connect them. I append 

 a literal translation of Eosa's view as to this relationship : — 

 " The Acauthodrilidae have the male pores on the posterior 

 margin of the clitellum, or beyond it ; and the clitellum is 

 constituted by a complete girdle, an arrangement which leads 

 to the first group, Eudrilidae and Perichaetidae. At other 

 times they have the male pores in the median region, or 



^ A " complete " clitellum signifies one in which the glandular substance 

 is developed equally all round the body, instead of only upon the dorsal and 

 lateral regions. As will be seen later (p. 262, footnote), there are reasons, 

 in my opinion, against making any such use of the clitellum in classification. 



2 I prefer to term these structures "atria," in order to fix their identity 

 with the atria in many of the aquatic genera {Of. Beddard, On the Structure 

 of Three New Species of Earthworms, etc. — Q. J. M. S., vol. xxix,, pt. 2, 

 pp. 117-128. 



^Contributions to the Anatomy of Earthworms, etc. — Q. J. M. S. , vol. 

 XXX., p. 473. 



