76 Annals of the South African Museum. 



leg, so that nothing remains to indicate the spot where it was 

 situated, except a minute brick-red orifice. Such retracted papillae 

 are frequently found in spirit specimens, and I have also observed 

 the actual process in the living animal. In its retracted condition 

 the central papilla lies at the bottom of a deep cavity, which opens 

 externally by means of a small brick-red orifice, exactly at the spot 

 previously occupied by the papilla (fig. 21). The wall (r./) of the 

 cavity is simply the ring-fold invaginated and flattened out. The 

 latter is, therefore, not a permanent structure, but merely produced 

 by the evagination of the sac containing the retracted papilla. 



The epithelium of the ring-fold and of the basal part of the papilla 

 resembles that of the ordinary papillose skin of the leg, each cell 

 having its convex or conical free end covered with numerous 

 minute prickles. In its distal part, however, the papilla, although 

 provided with scales, is not echinate on the surface, and the cuticula 

 is distincter and thicker (fig. 21). 



It is interesting to note that the ring-fold and papilla may be 

 completely retracted, while the basal organ remains fully expanded; 

 or both may be retracted together, in which case the ventral surface 

 of the leg presents an appearance scarcely differing from that of the 

 leg of a Peripatopsis. 



I have never found any external trace of the papilla and ring-fold 

 in any female specimen in the collection, and in two females which 

 were sectioned they, as well as the crural glands, proved completely 

 absent from all the legs examined (viz., the 6th to 16th pairs inclu- 

 sive). I feel fairly certain that these organs are at least never 

 present in the form in which they occur ia the male, although from 

 certain facts concerning their occurrence in Peripatopsis, which will 

 be presently discussed, it appears quite possible that they may 

 sometimes occur in a more rudimentary condition. 



Peripatopsis. — The crural glands in this genus have been described 

 by Balfour (1883), Moseley and Sedgwick (in Balfour, 1883), and 

 Miss L. Sheldon (1889). They are dimorphous in the male, those 

 of the pair of legs which immediately precedes the genital segment 

 in this sex being enormously elongated and reaching forward to the 

 middle of the body, while those of the other legs are small and lie 

 wholly within the cavity of the legs. 



I have examined sections of both kinds of glands in the males of 

 capensis and balfouri. They resemble those of Opisthopatns but 

 differ in the length of the glandular pouch, which is intermediate in 

 size in the latter genus between the two kinds found in the former. 



The duct of the enlarged glands of the pregenital pair of legs is 



