70 Annals of the South African Museum. 



midway between the hind end and the penultimate pair. The 

 ■condition in the latter case scarcely differs from that in Opisthopatus. 

 Similarly in the genus PeriiJatoides there is a certain amount of 

 variation amongst the different species. In P. nova-zealandia, for 

 instance, the postgenital part of the body is often relatively con- 

 siderably larger than in our specimens of P. leuckarti var. orientalis 

 (Fletcher). 



5. The coxal organs. 



The curious organs of unknown function to which Bouvier applied 

 this name had been observed hitherto only in Peripatus, and their 

 presence in Opisthopatus, therefore, forms a most interesting feature 

 of the latter genus. 



Externally they are best examined in specimens which have been 

 distended by drowning in water,''' and a description of their appear- 

 ance and distribution in a large male from Eichmond, prepared in 

 this way, may serve as a typical case. 



Fig. 14 is a carefully draWn view of the ventral surface of one of 

 the legs and shows the coxal organ (ex) in its fully expanded con- 

 dition, as it always appears in drowned specimens. It consists of 

 a somewhat four-sided area of smooth ectoderm, occupying a large 

 part of the ventral basal portion of the leg and protruding con- 

 siderably above the level of the surrounding tissue in the form of 

 a convex cushion or bolster.! There are no ordinary (primary) 

 papillae on this area, and even the minute secondary papillae, which 

 are so plentiful on the surrounding surfaces, are here entirely absent. 



* Such specimens may subsequently be advantageously preserved in formaline, 

 but drowned specimens do not yield as good material for sections as do ordinary 

 spirit specimens. 



f In this male specimen there are normally 4 rows of larger papillae between 

 the proximal pad and the distal edge of the coxal organ, about 4 rows on each 

 side of the organ, and a single row, or at least space for a single row, between its 

 proximal edge and the nephridial aperture (n). All of these rows have been care- 

 fully drawn in fig. 14. In most females, and to some extent in some of the 

 males, rows of smaller papillfe are intercalated between these 8 to 9 rows so as to 

 alternate with them. The total number of rows, therefore, between the proximal 

 pad and the distal edge of the coxal organ varies from 4 (in some males) to about 

 6 or 7 (in most females). In the male from which fig. 14 was sketched the 2nd, 

 4th, 6th, and 8th rows, counting from the spinous pad, contained the largest 

 papillse and constituted the paler bands, while the 1st, 3rd, 5th, and 7th rows 

 formed the dark bands, when such were present. In the females these 8 rows are 

 easily recognised if this be borne in mind, in spite of the intercalated rows. 

 I have never observed an intercalated row between the distal row of (dark) 

 papillse and the second row of larger (pale) papillse in any specimen, although 

 sometimes the row of dark distal papillse may be quite obsolete ventrally in the 

 middle. 



