236 Proceedings of the Royal Physical Society. 



necessary to consider the terricolous forms as forming two 

 groups, which are each equivalent to various groups, such 

 as Tubificidie, etc., into which the limicolous forms may be 

 suitably divided. To a certain extent, therefore, it will be 

 seen that my views accord with those recently expressed by 

 Eosa ;^ but before criticising the scheme propounded by the 

 Italian naturalist and expounding my own, it may be useful 

 to give a short resume of previous opinions. 



It is impossible to commence earlier than Perrier,^ whose 

 views were the result of the study of a larger number of 

 forms than had been previously investigated by any one of 

 his predecessors except Kinberg.^ But Kinberg's scheme of 

 classification cannot be considered seriously, as it took 

 account only of certain external characters, the number and 

 arrangement of the seta3, and one or two other points of even 

 less importance. The reader is therefore referred at once to 

 Kinberg's paper, or to an abstract of it, in vol. iii. of the 

 " Zoological Record " (p. 597). 



M. Perrier, distinguishing earthworms as a group equiva- 

 lent to that of the rest of the Oligochseta,^ divided them into 

 three divisions, mainly fixed by external characters, which 

 were believed, however, to be in harmony with internal 

 organisation — 



(1.) Lombriciens Anteclitelliens — 



Male reproductive pores in front o/ clitellum. 



(2.) L. Intraclitelliens — 



Male reproductive pores within clitellum. 



(3.) L. Postclitelliens — 



Male reproductive pores behind clitellum. 



To these three a fourth — L. AclitelUens, to include Monili- 

 gaster, without a clitellum — was somewhat doubtfully added. 

 Later on, M. Perrier^ expressed himself with regard 



1 Nuova CLassificazione dei Terricoli— Boll. Mus. Zool. Torino, No. 41, 

 vol. iii. (1888). 



2 Memoires pour servir h I'histoire des Lombricieiis terrestres — Nouv. 

 Arcli. d. Mus., t. viii. (1872). 



3 Annulata nova— tEfv. af K. Vet. Akad. Forh., 1866, p. 97. 



* lltudes 8ur I'Organisation des Lombriciens terrestres : iv. Organisation 

 des Pontodrilus [E. P.]— Arcb. do Zool. Exp., t. ix., 1881, p. 236, note. 



