THE ANATOMY AND DEVELOPMENT OF PERIPATUS NOVAE-BRIT ANNIAE. 



7 



here of the aperture of a segmental organ whose usual place is at the base and 

 not near the extremity of the 6th leg, looks very much like atavism. Perhaps the 

 enlarged nephridia corresponding to the 4th and 5th legs are the vestiges of an 

 ancestral form in which all or most or some only of the ordinary nephridia served 

 for the passage of the genital products to the exterior. If there were sufficient grounds 

 for accepting this as a legitimate hypothesis it would afford an explanation of, or at 

 least throw light on, the great contrast there is between the anteriorly-placed genital 

 pores of the Diplopoda and the terminal posterior pores of the Chilopoda. 



iv. Segmental grooves. At the bases of the legs on the ventral surface there 

 is, in the older individuals, a series of not very well-defined grooves at. the inner ends 

 of which the segmental organs open to the exterior. They are characterised by a 

 rather deeper pigmentation but by no other special feature. They occur at the bases 

 of the 4th and 5th legs although here the segmental organs do not open into them. 

 These grooves are therefore not so distinctive as are the corresponding structures in 

 P. capensis and in P. edwardsii. In the latter they are separated from the apertures 

 of the nephridia (Gaffron). 



v. Crural glands. There are no white papillae on the ventral side of the legs 

 in the male such as occur in most other species of Peripatus. These papillae, when 

 they occur, bear at their tip the aperture of a crural gland. But crural glands may 

 occur without having their external apertures borne on white papillae. In P. novae- 

 britanniae as in P. novae- zealandiae (Sheldon 22) there are no crural glands in either sex. 



Wherever they occur they are found only in the male except in P. capensis where 

 they are said to occur in the female also (Sheldon 22). Without denying their occasional 

 existence in the female P. capensis I may say that I have failed to find them present 

 so far as I have looked for them. They are therefore in any case not always present, 

 and I should doubt, on a priori grounds, if they normally occur in the female. There 

 is a well-developed " fat-body " to be seen in sections through legs of female P. capensis 

 and perhaps this has been confused with a crural gland. 



In the male P. capensis the crural glands are well-defined structures and, as may be 

 gathered from Balfour (2) and Sheldon (22), they are present in all the legs except those 

 of the first pair. Only the crural glands of the last pair of legs in the male P. capensis 

 have their external apertures borne on white papillae and these constitute the unfailing- 

 external sign of the male in this species. 



In P. leuckarti of Australia, of which Fletcher (5) has clearly established the 

 existence of three distinct varieties, viz., typica, orientalis and occidentalis, white papillae 

 may occur in the male on each leg of the first pair only, or of the last pair only, or 

 of all or only some of the pairs with the exception of the first, or of the first five 

 (Fletcher). Here again, however, Fletcher notes that crural pores may occur in the 

 absence of white papillae. 



In P. edwardsii, Gaffron (6) and Sedgwick (19) have shown that white papillae 

 occur on certain of the posterior legs of the male, often two such papillae on one 

 leg. Thus Gaffron figures a specimen with two papillae on each of the legs of the six 

 praegenital segments and one each on those of the 7th praegenital segment. The genital 

 and post-genital segments never have white papillae in this species. 



