ON PERICHAETIDAE. 



207 



gap; 54 of them on segment VI, 68 on segment XIX. 

 The ventral setae are straighter and longer than the dorsal 

 ones. No setae on clitellum. First dorsal pore in the in- 

 tersegmental groove XII/XIII. Several small spermathecal 

 pores in a transverse row, in the grooves between segments 

 V and VI, VI and VIL Oviducal pore single, on an oval 

 area upon segment XIV. Male pores , on prominent conical 

 papillae, formed by a longitudinal crescent fissure with 

 crenulated lateral margin. In the interspace between the 

 male pores 12 to 14 setae; their number is somewhat 

 variable, and depends on the development of the papilla. 



The number of pairs of copulatory papillae on the suc- 

 ceeding segments is different in several individuals. In most 

 of them there are four pairs of papillae on segments 

 XIX — XXII ; but this number can increase to eleven 

 pairs and decrease to a single one. 



On comparing the number of papillae of different in- 

 dividuals they will prove to form an almost uninterrupted 

 series, as demonstrated by the following table: 



The first specimen (a) is characterized by the presence 

 of 11 pairs of papillae on segments XIX — XXIX; a second 

 specimen (6) however possesses 9 pairs on segments XIX — 



Notes from the Leyden. Museuin , Vol. X.X. 



