Tlie Anatomy of Opistliopatus cinctipes. 93 



number of ordinary papillae, bearing each a spine at the apex, but in 

 the male these papillse, although still distinguishable, were very low, 

 giving the eminence under a low magnifying power the appearance 

 of a true spinous pad. This seems to constitute an easy means of 

 distinguishing the sexes in this species, although Sedgwick states 

 that they are externally indistinguishable. The orifice was also 

 more gaping in the female than in the male. 



Peripatopsis. — In the synopsis of the characters of this genus, 

 given in my previous paper (1899, p. 335), the genital opening is 

 described as longitudinal but never transverse. This statement was 

 based on an examination of the females, and was intended for com- 

 parison with the female of Opisthopatus, but does not apply to the 

 males of two species, viz., P. capensis and P. moseleyi. 



I have since then examined by means of horizontal sections and 

 otherwise a number of males of P. capensis, and find that the 

 genital opening in this species very closely resembles that of the 

 male of 0. cinctipes. The orifice is very distinctly cruciform with 

 four equal arms, situated between four prominent and well-developed 

 spinous pads. The two anterior pads are slightly larger, and are 

 placed between the rudiments of the legs of the genital segment, 

 while the two posterior pads lie behind them in such a manner that 

 the transverse part of the orifice, if produced, w^ould just touch the 

 hind surface of these legs. The cruciform orifice leads into the 

 ductus, the lumen of which, like that of 0. cinctipes, also appears 

 cruciform in cross-section in its most posterior part. 



In P. moseleyi the condition is exactly similar. 



In the females of Peripatopsis the sexual orifice is essentially a 

 longitudinal opening, the lips of which bear ordinary papillse but no 

 spinous pads. Occasionally, however, the lips are bisected by a 

 shallow groove, but I have never observed a true cruciform opening. 



Peripatus. — I have not sufficient material of this genus for the 

 purpose of an investigation, but it may be mentioned that according 

 to Horst (1886, p. 39, pi. 2, fig. 4) the genital opening of Peripatus 

 sumatramts, Sedgw., is cruciform and situated between four tubercles 

 in the type specimen. 



From the above it is evident that the cruciform sexual opening is 

 the normal form in at least one or the other sex of some of the 

 species in each of the three Cape and Australasian genera, and may 

 be looked upon as the primitive condition, from which a transverse 

 or longitudinal opening has been derived in one of the sexes (mostly 

 the female) by the more or less complete reduction of the longi- 

 tudinal or transverse portion respectively of the opening. 



