The Anatomy of Opisthopatus cinctipes. 79 



In his recent paper on Peripatus, Bouvier (1900a) describes the 

 males of three species, in all of which he found these papillae. 

 These species are : — 



(1) P. sedgioicki, Bouv., in which, according to Gaffron (1885), 

 Sedgwick (18886) and Bouvier (1900a), the papillae occur on the 

 7 to 8 pairs of legs immediately preceding the genital segment. 

 There are generally two present on each leg, except on the anterior 

 ones, where they are present singly (see Sedgwick, 1888&, pi. 20, 

 fig. 22). 



(2) P. doniinicce, Pollard, and its var. antiguensis, Bouv., in which 

 Bouvier found two papillae on each leg of the two pairs immediately 

 preceding the genital segment (pp. 422 and 431, pi. 5, figs. 4 

 and 5). 



(3) P. trinidadensis Sedg., in which Bouvier found two papillae on 

 each leg of the antepenultimate pair and frequently also of the pre- 

 ceding pair (p. 487, pi. 6, fig. 6). 



In every case, therefore, these papillae and doubtless also the crural 

 glands are absent from the postgenital and genital pairs of legs, but 

 are present in the legs of the pair immediately preceding the genital 

 segment and generally also in a varying number of the legs preceding 

 these. The papillae are very large and conspicuous and are always 

 situated along the posterior border of the coxal organ. The distal 

 one, which is placed next to the distal part of the hind margin of the 

 coxal organ not far from the proximal spinous pad, coincides almost 

 exactly in its position with those of Opisthopatus (compare my fig. 14 

 with those of Sedgwick and Bouvier mentioned above). It is a,lso 

 interesting to note that when only one papilla is present on a leg it 

 is, according to Sedgwick, always the distal one. 



Bouvier gives us some interesting information concerning the 

 structure of these papillae. He says they are formed of an annular 

 pad-like elevation, in the middle of which is a projecting tubercle 

 with what appears to be an orifice in its centre. This refers to 

 P. trinidadensis, but his figures of P. dominicce var. antiguensis show 

 a similar structure. Now the resemblance of this structure to the 

 evaginated ring-like fold and central papilla of Opisthopatus is so 

 striking that one cannot but suspect that these organs are constructed 

 on the same plan in both genera and that they may prove to be 

 retractile in Peripatus as well. In Sedgwick's figure of this organ in 

 P. sedgioicki, Bouv., the large outer ring-pad alone is shown, with a 

 depression in the centre, the whole resembling in appearance the 

 ring-fold in Opisthopatus, when the central papilla has been com- 

 pletely retracted. Moreover, in one of Gaffron's figures (1885, 



