The Classification and Distribution of Earthworms. 263 



form of the sete are occasionally, although not very 

 commonly, met with. In Fcrichaita Houlleti the clitellar 

 setae are very distinctly different in form from the rest.^ 

 But the most striking resemblance is shown by Deodrilus,'^ in 

 which all the sette of the body are ornamented, though in 

 a way rather different from that of Rhinodrilus and other 

 Geoscolecine genera. It is remarkable also that among the 

 Cryptodrilidne only — in the genera Deodrilus and Typhosus — 

 has the prostomium disappeared : ^ this is a character which 

 distinguishes no less than three genera of Geoscolecini — 

 viz., Urochceta, Biachceta, and Onychochceta — and is unknown 

 elsewhere. 



If the characters of the clitellum are by any one considered 

 necessary, then Deodrilus fulfils the required conditions ; for, 

 as I hope to point out later, the clitellum is constructed on 

 a plan which is exactly that of Acanthodrilus.^ The presence 

 of atria is one of the distinguishing features of the Acan- 

 thodrilini, being, without any exception, universal in that 

 group. Is it not possible that the so-called atria of Criodrilus ^ 

 and Geoscolex ^ may represent these same structures in course 

 of degeneration ^ ? Unfortunately we have no histological 



^ Beddard, Contributions to the Anatomy of Earthworms — No. III. 

 Note on the Genital Setae of Perichceta Houlleti (P. Z. S., 1887, p. 389). The 

 woodcut illustrating those setfe is not so good as it might be. 



^ A description of this genus, which is a native of Ceylon, will appear in ^ 

 forthcoming number of the *•' Quarterly Journal of Microscopical Science." 



^ I have not myself been able to find a prostomium in this genus ; but I 

 may possibly have failed to see one, since Bourne (On certain Earthworms 

 from Western Himalayas, etc., J. A. S. B., vol. Iviii., p. 110) has lately 

 described and figured a prostomium, capable of being largely retracted in a 

 new species of the genus T. Masoni. 



^ Trigaster Lankestcri (Benham, Studies on Earthworms, No. II. — 

 Q. J. M. S., vol. xxvii.) has been regarded by Rosa as having an incomplete 

 clitellum. Benham is not perfectly precise upon this point in his paper, but 

 he has informed me since, that in front of the generative pores, as in other 

 Acanthodrilidae, the clitellum is complete. 



^ Rosa, loc. cit. (on p. 258), p. 12, fig. 8, atr. 



^ Perkier, Mem. pour servir a I'histoire, etc., loc. cit. (on p. 236). 



^ Michaelsen's Callidrilus appears also to be a connecting link between the 

 Cryptodrilidffi and Geoscolecini ; its general organisation conforms to that of 

 the former group, but it has, as in Microchccta, numerous minute spermathecte 

 in segment xiii. This is one of those facts which point to the Geoscolecini 

 being a composite group derived from several stocks. 



