208 ON PERICHAETIDAE. 



XXVII and a single papilla on segment XXVIII at the right 

 ventral side, so we may conclude that of the tenth pair 

 the left one is not developed. In a third specimen (e) we 

 find 9 papillae at the left and 3 at the right ventral side, 

 forming a complete pair only on segments XIX, XXVI 

 and XXVII, while on the interposed segments (XX — XXV) 

 the right papilla is not developed. Next follows an inter- 

 ruption in the series , for specimens with 7 and 8 pairs 

 have not been observed by myself, but an individual (d) 

 collected on the Liang Koeboeng showed 6 pairs on 

 segments XIX — XXIV. Another specimen {e) presents 4 

 pairs of papillae on segments XIX — XXII and a single one, 

 at the right side , on segment XXIII ; it is likely that of 

 the last pair the left papilla was not developed. In another 

 individual there are no papillae on the anterior segments 

 XIX and XX, but segments XXI and XXII show a pair 

 of them and segments XXIII a single one ; it may be 

 presumed that in this specimen both anterior pairs of 

 papillae and one of the last pair are checked in their 

 development. Specimens with 4 pairs of papillae on segments 

 XIX — XXII, like ƒ, are very common; even in immature 

 individuals, without clitellum, these papillae are recognizable. 

 A specimen, that has only two pairs of papillae on 

 segments XXI and XXII, but wants those on the two 

 preceding ones, belongs to the same category. In the 

 worms from Nanga raoen there are but 3 pairs of papillae 

 visible on segments XIX — XXI (g). A few specimens (A) have 

 only 2 pairs of papillae on segments XIX and XX ; and 

 in one individual (i) only a single pair of them on segment 

 XIX is present. The papillae have a transverse oval shape 

 and are situated just in front of the circle of setae, 

 which sometimes are pushed from their place ^). 



The spermathecae lie in segments VI and VII ; in most 

 specimens there are more than one pair in each segment, 



I) For an account of their structure, as also for more details of the inter- 

 nal anatomy, see my paper ,.on the earthworms of the Dutch Scientific Expedi- 

 tion to central Borneo." 



Notes from the Leyden JVIuseuixi, Vol. XX- 



