1892.] OF THE GENUS PERICH^TA. 16/ 



The atrium is not furnished with a distal sac. 



There are two pairs of spermatheccB, which lie in segments ti. and 

 vii. ; the appendix is a tube of uniform calibre 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. 



Perich^ta 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 somewliat 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 prechtellar somites is 18 mm.; 

 the clitellum itself measures 4 mm. The number of segments 

 is 78. 



In this individual — which I call u — setae 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 setae upon the last segment of the clitellum is small, about half 

 a dozen. 



In the second individual (6) the number of setae upon the last 

 segment of the clitellum is greater than iu a. 



In the third individual (c) the number of setae 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, 

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

 lies within the circle of setae 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 

 iu the disappearance of the setae belonging to the clitellar segments. 

 Iu immature worms setae are always present upon the clitellar 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 clitellar setae coincide with 

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

 number of spermathecae. 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 papillae. Hence I 



