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



relMtion 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 Perichcette there 

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

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

 occurs to nie is Perichctta taprobance described in the present 

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

 but differs from Perichceta 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 Perichceta described in the 

 present paper the setae of the eight anterior segments are very 

 much larger than those upon the 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 

 taprobance, 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 the 

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

 but there iieuerally 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 Perichtetce it was a nearly sufficient definition to state 

 merely the number and position of the spermathecSB. 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 which record new species of Perichceta. So far as we know 

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

 of systematic importance : — 



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



(2) The number of setse upon tlie segments. 



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



xvi.^ 



(4) Whether the setae are jiresent 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 hke to take this opportunity of calling attention to the 

 importance of illustrating these and other Earthworms by accurate 



1 " On Megascolex csruleus, Templeton, &c.," Q. J. Micr. Sci. vol. xxxii. 

 ^ My attention was directed to the iuiportauce of this point by Prof. Bourae's 

 paper upon Megascolex ccsruleus (Q. J. Micr. Sci. vol. xxxii. p. 49). 



