THE ANATOMY AND DEVELOPMENT OF PERIPATUS NOVAE-BRITANNIAE. 15 



In P. edwardsii according to Gaffron the unpaired portion of the male genital duct 

 attains the remarkable length of 7 centimetres. 



In P. capensis the unpaired portion of the duct is much shorter than in P. edwardsii, 

 but is still a fairly long bent tube which does not occupy the median line and is 

 quite asymmetrical (Moseley 14 ; Balfour 2). According to Moseley's account, which was 

 confirmed by Balfour, the unpaired terminal duct of the Cape species appears to be 

 " a continuation of one of the ducts only, the other duct being cut short and entering 

 " from the side.' 1 It may be either the right or the left vas deferens which is directly 

 continued into the terminal duct. Moseley goes on to say that " from the way in which 

 " one duct passes under the nerve-cord [i.e. nerve-cords] and not the other, and from 

 " the curious sharply-turned loop formed by this latter duct on entering its fellow, it 

 " would appear that the original condition had been almost exactly similar to that existing 

 " in the female organs." (Moseley 14, p. 709.) 



Fig. 4 a and b. Terminal portions of the male genital ducts of P. capensis (a) and of P. novae-britanniae (b). 



The shaded structures represent the ventral nerve-cords which pass into each other behind by the supra- 

 rectal commissure ; A is after Moseley, B is original. 



Thus in the symmetrical manner of formation and in the short median course of 

 its ductus ejaculatorius, the male of P. novae-britanniae exhibits a distinctly primitive 

 feature as compared with all species hitherto described. This is a matter of some 

 importance in view of the fact that hitherto "no gradation of structure within the 

 genus" (Sedgwick) had been observed. 



In P. novae- zealandiae according to Miss Sheldon (22) the unpaired portion of the 

 male genital duct is much longer than in P. capensis and closely resembles that of 

 P. edwardsii. It seems to me that the length of the unpaired portion of the genital 

 duct is in correlation with the production of spermatophores. In P. capensis (Sedgwick, 

 Sheldon) the spermatophores are little oval bodies consisting of a thin structureless 

 case filled with spermatozoa. 



In P. novae- zealandiae (Sheldon 22) the posterior part of the duct contains 



