DESCRIPTIONS OF GENERA AND SPECIES 



391 



the others ; P. houUeti, as I have pointed out, agrees with P. biserialis and P. acystis 

 in this character; Hoest has described the whole of the setae on the ventral side 

 of the body in Ferichaeta as being very large as compared with those on the dorsal side. 

 (3) T^e presence or absence of the setae on the clitellum is a matter which has 

 been often overlooked ; and yet it offers a very good character for the distinguishing 



Fig, 44. 



CDEVES SHOWING THE NUMBEK OF SETAE ON THE ANTEEIOE SEGMENTS OF 



CERTAIN PEEICHAETA. 



[The segments are numbered above, the number of setae in tens on the left.] 



«. P. taprobanae, 6. P. dyeri. c. P. dnmsis. d. P. bariadensis. 



e. An unidentified species from Hong-Kong. /. P. bermudenm. 



of species ; the degree to which the setae are developed is also important ; in P. tapro- 

 banae, for instance, the setae are present, and to the full number, on all the segments 

 of which the clitellum is composed ; in P. indica we have the opposite extreme ; 

 there are in this species no setae at all upon the clitellum ; this statement, of 

 course, refers to the mature worm ; when the clitellum is undeveloped, the segments, 



