258 Proceedings of the Royal Physical Society. 



Observation. — I am doubtful at present about Criodrilus. 

 The structure of this worm has been investigated by 

 Vejdovsky/ Eosa,^ Oerley,^ Benham/ and Collin.^ 



Is Eosa's group of the Geoscolecidae a natural one ? It 

 is thus defined by him : — " Male pores within the clitellum 

 between the dorsal and ventral setse, occupying segments, 

 or intersegmental spaces, very variable in position. Cli- 

 tellum usually saddle-shaped, varying in length and posi- 

 tion. Setae 8 per segment, disposed in pairs, or distant, or 

 in different arrangements, often varying in the anterior and 

 posterior segments. Copulatory setae longer than the others, 

 and of a different form. The gizzard (or gizzards) placed 

 anteriorly. Sperm sacs one or two pairs. ISTo prostates or 

 penial setse." 



The following tabular scheme indicates the chief struc- 

 tural points which characterise the ten genera about which 

 alone we have any anatomical knowledge. Eosa refers Kin- 

 berg's genera^ — Geogenia, Tritogenia, and Eiorydame, besides 

 Schmarda's '^ Pontoscolex — to this group. 



^ System und Morphologie der Oligochseten. Prag, 1884, passim. 



^ Sul Criodrilus Zacww77i Studio Zoologico ed Anatomico — Mem. R. Ace. Sci. 

 Torino, ser. 2, t. xxxviii. (1887). 



^ Morphological and Biological Observations on Criodrilus lacumii — Q. J. 

 M. S., vol. xxvii. (1887), p. 551. 



^ Studies on Earthworms — III. Criodrilus lacuum, Hoffmeister (Q. J, M. S., 

 vol. xxvii., 1887, p. 561). 



^ Criodrilus lacuum, — Zeitschr. wiss. Zool., Bd. xlvi. (1888). 



6 Annulata nova— (Efv. af K. Vet. Akad. Forh. (1866). 



^ Neue "Wirbellose Thiere gesammelt auf einer Reise um die Erde, vol. ii. 

 (1861), p. 11. 



