Tlic Classification and Distrihttion of Earthworms, 237 



to the connection between the Intraclitellians and Post- 

 clitellians as follows : — " Euclrilus, which we have placed, 

 in our Rechcrches pour servir d Vhistoire des Lomhriciens 

 terrestres, among the intraclitellian earthworms, appears to be 

 transitional between this group and that of the Fostclitellians, 

 if we only consider the extent of the clitellum, which in our 

 species is prolonged beyond so as to reach the male repro- 

 ductive pores ; in reality, their organisation is that of the 

 * Fostclitellians,' and we should place them at the head of that 

 group immediately after the Intraclitellians." 



The points to which M. Perrier refers here are chiefly 

 the atria, which he compares in the text to those of Ponto- 

 drihis. 



Further researches did not tend to confirm the naturalness 

 of Perrier's classification, except as regards the first and 

 fourth groups.^ I myself have pointed out that Megascolex 

 coeruleus,^ otherwise so closely allied to Perichceta, has " intra- 

 clitellian" male reproductive apertures. 



Acanthodrilus is a genus of which, according to Horst, 

 Perrier, myself, and others, some species ought to be referred 

 to the second, others to the third, of Perrier's groups as 

 defined above. 



Other instances of a like kind show that a hard and fast 

 line cannot be drawn between the Postclitellians and the 

 Intraclitellians as regards the extent of the clitellum. 



M. Perrier's classification has been attacked, and, in so far 

 as he laid most stress upon the relations of the male pores 

 to the clitellum, justly attacked, according to my way of 

 thinking. 



It will be noticed, however, in the course of the present 

 paper, that all his groups — after removing only the Eudrilid?e 

 — are perfectly natural assemblages if they are regarded from 

 other points of view, to some of which, indeed, such as the 

 presence of atria, he refers himself. One of the principal 

 relations upon which I insist in this paper is the necessary 



^ Dr Rosa himself {loc. cit, p. 9) regards the Moniligastridae as a distinct 

 family. 



2 On the Anatomy and Histology of Pleurochceta Moseleyi — Trans. Koy. Soc. 

 Edin., vol. XXX. 



