92 MERISTIC VARIATION. [part i. 



moreover, in some of the species the number appears to be very 

 constant for the species, in the case of others, great individual 

 variation is seen to occur. Sedgwick's observations in the case of 

 P. edwardii shew conclusively that these variations cannot be 

 ascribed to difference in age. There is besides no ground for sup- 

 posing that increase in the number of legs occurs in any species 

 after birth, and it is in fact practically certain that this is not the 

 case. In Peripatus capensis, which was exhaustively studied by 

 Sedgwick, the appendages arise in the embryo successively from 

 before backwards, the most posterior being the last to appear, and 

 the full number is reached when the embryo arrives at Sedgwick's 

 Stage G. The following is taken from the list constructed by 

 Sedgwick from all sources, including his own observations. As 

 the bibliography given by him is complete and easily accessible 

 it is not repeated here, and the reader is referred to Sedgwick's 

 monograph for reference to the original authorities. 



Sedgwick, A., Quart. Jour. Micr. Sci. xxviii., 1888, pp. 431 — 

 493. Plates. 



South African Species. 



P. capensis : 17 pairs of claw-bearing ambulatory legs (Table 

 Mountain, S. Africa). 



P. balfouri : 18 pairs of legs, of which the last pair is rudiment- 

 ary (Table Mountain, S. Africa). 



Sedgwick has examined more than 1000 specimens from the 

 Cape, and has only seen one specimen with more than 18 pairs of 

 legs. This individual had 20 pairs, the last pair being rudiment- 

 ary. It closely resembled P. balfouri, but differed in the number 

 of legs and in certain other details (q. v.); Sedgwick regarded this 

 form provisionally as a variety of P. balfouri. 



P. mosleyi : 21 and 22 pairs of legs: near Williamstown, S. 

 Africa. The specimens with 22 legs were two in number and were 

 both females. They differed in certain other particulars from the 

 form with 21 legs, but on the whole Sedgwick regards them as a 

 variety of the same species. 



P. brevis (DE Blainville): 14 pairs of legs. (This species not 

 seen by Sedgwick.) 



Other species from S. Africa which have been less fully studied 

 are stated to have 19, 21 and 22 pairs of legs respectively. 



In all South African forms, irrespective of the number of legs, 

 the generative opening is subterminal and is placed behind the 

 last pair of fully developed legs (between the 18th or rudimentary 

 pair in P. balfouri). Sedgwick, pp. 440 and 451. 



Australasian Species. 



P. v one- Zealand ice. 15 pairs of legs. New Zealand. 

 P. leuckartii. 15 pair of legs. Queensland. 

 In both of these species the generative opening is between the 

 last pair of legs. (Sedgwick, p. 486.) 



