154 MR. F. E. BEDDARD ON WORMS [Feb. 16, 



relation of these numbers to one another varies with other important 

 characters rather than the actual numbers themselves." 



Prof. A. G. Bourne ^ considers that in all true Ferichcet(E there 

 are setae between the male pores. So far as my own experience 

 goes I agree with Prof. Bourne. The only possible exception that 

 occurs to me is Perichcuta taprobancB described in the present 

 paper (on p. 163). That species has setse between the male pores, 

 but differs from Perichtsta in a few other points to which I direct 

 attention. Another point which appears to me to be of importance 

 is the size of the setae upon the anterior as contrasted with the 

 posterior segments ; in all the species of PericJiceta described in the 

 present paper the setae of the eight anterior segments are very 

 much larger than those upon tbe segments which follow ; there is 

 an abrupt break at the end of segment viii. ; up to this point the 

 setae get gradually larger upon successive segments. In Perichceta 

 ta-prohance, which may perhaps be a distinct genus, there is no such 

 marked difference between the segments in front of and those behind 

 the eighth. Although there is a sudden diminution in size of tbe 

 setae there is not always a corresponding increase in their numbers, 

 but there generally is an increase. 



So much, then, for the generic distinctions of Perichceta. 



As to the species there exists already some little confusion, and I 

 am not prepared to guarantee absolutely the novelty of the species 

 described in the present paper. When there were only a very few 

 species of the genus known, their discrimination was a much easier 

 matter than it is now; at the time that Perrier wrote his first 

 descriptions of Perich^tce it was a nearly sufficient definition to state 

 merely the number and position of the spermathec^. There are 

 therefore a good many points, now known to be of systematic 

 importance, which are omitted or not clearly set forth in some of the 

 papers wbich record new species of Perichceta. So far as we know 

 at present, the following are the principal external features which are 

 of systematic importance : — 



(1) Whether the ventral setse are larger than the rest. 



(2) The number of setae upon the segments. 



(3) Whether the clitellum includes the whole of segments xiv.- 



xvi.^ 



(4) Whether the setse are present or absent from some or all of 



the clitellar segments; and if present whether they are 

 modified (as, for instance, in Perichceta houlleti). 



(5) The number and arrangement of the anterior and posterior 



genital papillae. 



(6) The position of the atrial pores upon the xviiith segment, i. e. 



whether they are more lateral or ventral. 



(7) Colour and size (including number of segments). 



I should like to take this opportunity of calling attention to the 

 importance of illustrating these and other Earthworms by accurate 



1 " On Megascolex c<Bruleus, Templeton, &c.," Q. J. Mici'. Sci. vol. xxxii. 

 ^ My attention was directed to the importance of this point by Prof. Bourne's 

 paper upon Megascolex cceruleus (Q. J. Micr. Sci. vol. £cdi. p. 49), 



