The Classification and Distribution of Earthiuorms. 245 



Eosa's reasons for regarding the Acanthodrilidie as the 

 most primitive existing forms are the following : — • 



(1.) The frequent doubling of the dorsal vessel/ which 

 seems, from the observations of Kowalevsky and 

 Vejdovsky, to be a persistent embryonic trait. 



(2.) The presence in A. dissimilis ^ of two pairs of ovaries 

 corresponding to the two pairs of testes. 



(3.) The comparative independence of the two vasa 

 deferentia of each side. 



(4.) (This is queried) the presence of 8 nephridia per somite 

 in A. niultiporus. 



As regards (1.) it is undoubtedly true that a good number 

 of species of Acarithodrilus (four or five) show the peculiarity 

 mentioned. But this same doubling of the dorsal vessel occurs 

 in Megascolex cceruleus^ and in Microchceta Bappii,'^ in Deino- 

 drilus Benhami^ and in Teleudrilus Ragazzii.^ It is, however, 

 more frequent in the Acanthodrilidse than in other families. 



(2.) The rudiment of a second ovary (in segment xii.) 

 seems, from the researches of Bergh,^ to be so often met with 

 in Lumhricus, that I am not disposed to lay much stress upon 

 this character as indicative of the low position of Acantho- 

 drilus. Furthermore, I have shown some reasons for think- 

 ing that tivo fully developed ovaries are distinctive of 

 Eudrilus.^ 



^ Beddard, On the Specific Characters and Structure of certain New 

 Zealand Earthworms— P. Z. S., 1885, p. 821. 



2 Ibid., p. 828. 



^ Beddard, On the Anatomy and Histology of Fleurochceta Moseleyi — • 

 Trans. Roy. Soc. Edin., vol. xxx., p. 481. 



* Beddard, On the Anatomy and Systematic Position of a Gigantic Earth- 

 worm from the Cape Colony — Trans. Zool. Soc, vol. xii., p. 70 ; and 

 Benham, Studies in Earthworms, No. I. — Q. J, M. S., vol. xxvi. 



5 Beddard, On Three New Species of Earthworms, etc.— Q. J. M. S,, 

 vol, xxx. 



^ Rosa, Lombrichi delle Scioa — Ann. Mus. Civ. Geneva, ser. 2, vol. vi. 

 (1888), pi. ix., fig. 2. 



^ Geschlechtsorgane der Regenwiirmer — Z. wiss. Zool., Bd. xliv., pi. xxi,, 

 fig. 10, s. 



^ Further Notes upon the Reproductive Organs of Eudrilus — Zool. Anz., 

 No. 293 (1888). 



