1892.] OF THE GENUS PERICH^TA. 167 



The atrium is not furnished with a distal sac. 



There are two pairs oi spermathecce, which He in segments vi. and 

 vii. ; the appendix is a tube of uniform caUbre and is very nearly as 

 long as the pouch. In the case of one spermatheca, the appendix 

 is twisted at its commencement round the stalk of the spermatheca. 



Pertch^eta barbadensis, n. sp. 



In June of the present year I received from Kew Gardens five 

 living worms of the genus Perichceta, which were all of a reddish- 

 brown colour with a grey clitellum ; the iridescence of the cuticle 

 was very marked, on account of the dark pigment in the body-wall ; 

 when the worms were killed in weak alcohol, a quantity of yellowish 

 fluid was expelled from the dorsal pores. 



In spite of the close similarity in colour between all five specimens, 

 I believe that they are to be referred to two distinct species, of which 

 one — that which I call Perichceta barbadensis — is somewhat protean, 

 showing considerable variations, which I do not, however, regard, 

 for reasons which will be stated presently, as being of specific value. 

 I describe the second species subsequently (see p. 169). 



Two of the specimens were of about the same size, measuring 

 44 inches in length (when preserved in strong alcohol, after having 

 been killed in weak alcohol) ; the diameter in front of the clitellum 

 is 4 mm. The length of the preclitellar somites is 18 mm.; 

 the clitellum itself measures 4 mm. The number of segments 

 is 78. 



In this individual — which I call a — setse were present upon the 

 last segment of the clitellum (Plate IX. fig. 6) ; the chtellum itself in 

 all three specimens is fully developed upon all the segments xiv.-xvi. 

 and bears anteriorly the single median oviducal pore ; the number 

 of setse upon the last segment of the clitellum is small, about half 

 a dozen. 



In the second individual (b) the number of setae upon the last 

 segment of the clitellum is greater than in a. 



In the third individual (c) the number of setse upon the last seg- 

 ment of the clitellum is about as great as in b, but in addition the first 

 segment of the clitellum {i. e. no. xiv.) bears three, or possibly four, 

 setse on each side of the oviducal pore (Plate IX. fig. 7), which there 

 lies within the circle of setse of its segment, and not, as is usually 

 the case in the genus Perichceta, in front of the setse. It might be 

 supposed that these three individuals represented merely three stages 

 in the disappearance of the setse belonging to the ciitellar segments. 

 In immature worms setse are always present upon the ciitellar seg- 

 ments. I am not aware that any exact observations have been made 

 as to the time and manner of their disappearance in those species 

 which have, when adult, a clitellum devoid of setae. But in the 

 present species the differences in the ciitellar setse coincide with 

 differences in the genital papillae and also with difi'erences in the 

 number of spermathecse. But, as will be seen presently, it does not 

 happen that the worm with the fewest setae upon the clitellum has 

 the most marked development of the genital papillse. Hence I 



