6 THE ANATOMY AND DEVELOPMENT OF PERIPATUS XOVAE-BRITAXXIAE. 



II. Appendages. i. Antennae. I have made an observation with regard to the 

 antennae which may be worth recording, namely, that the annular spine-bearing ridges 

 increase in number during the life of the animal by the intercalation of new rings 

 between the older rings, so that the number of these rings is not a reliable specific 

 feature. In one individual I counted about 33 rings and in another about 50 

 [Fig. 6]. 



ii. Jams. The character of the jaws and oral papillae is adequately shown in 

 Fig. 5. The outer blade of the jaw is quite simple, while the inner blade is provided with 

 a variable number of minor teeth, generally about 5. In the absence of an accessory 

 denticle at the base of the outer jaw-blade, P. novae-britanniae resembles P. novae- 

 zealandiae as well as certain other Australian species or varieties (Fletcher 5). In 

 other Australian forms, e.g. in the larger Victorian species P. oviparus Dendy and in 

 the New South Wales variety P. leuckarti var. orientalis Fletcher, there is an accessory 

 denticle as in P. cape)isis and P. edwardsii. 



With regard to the inner ramus of the mandible or inner jaw-blade there is no 

 diastema between the first accessory denticle and the remainder of the series, such 

 as occurs in the Neotropical species (Sedgwick 19). 



iii. Xephridial apertures. The apertures of the enlarged segmental organs of 

 the 4th and 5th pairs of legs are placed in the centre of the proximal pad of these 

 legs [Fig. 7] and sometimes they divide the pad into two disconnected halves, and 

 sometimes again the two halves remain united by a narrow bridge passing distally 

 from one to the other. The division of the proximal pad of the 4th and 5 th legs 

 into two separate halves by the intercalation of the papilliform structure which carries 

 the nephridiopore is characteristic of P. capensis, according to Sedgwick. In P. novae- 

 zealandiae Sedgwick showed that the portion of the pad which carries the nephridiopore 

 is continuous distally with the rest of the pad. Finally in P. edwardsii the papilla 

 bearing the nephridiopore of the above segments is quite separate from the 3rd pad 

 and lies between the latter and the 4th pad. Thus in P. novae-britanniae, the 

 relations of the 4th and 5th nephridiopores sometimes approach the condition observed 

 in the Cape species and sometimes that of the Australian species. In Fig. 7, one 

 half of the proximal pad is seen to be independent while the other half is confluent 

 with the pore-bearing papilla. Another most interesting variation, which probably is of 

 frequent occurrence in this species, is the presence of a nephridial aperture in the 

 centre of the proximal .pad of the 6th leg in addition to those normally present on 

 the 4th and 5th legs. In no fewer than three individuals — all females — (I, III and 

 VIII) such an aperture occurs on the 6th leg of the left side only (Fig. 11). In 

 one individual — a male — (V) a nephridial aperture occurs in the middle of the proximal 

 pad of the 4th, 5th and 6th legs of each side of the body. As far as I was able 

 to observe the segmental organ of the 6th leg was not specially enlarged in those 

 cases where its external aperture was abnormally situated. The occurrence of a 

 distally-placed nephridial aperture on the 6th leg can hardly be regarded as a mere 

 instance of meristic repetition, because it does not involve the absolute number of 

 nephridial apertures but only the number of those which are placed in a certain 

 position. There must be some reason for such a position, and the occasional appearance 



