60 RICHARD KVANS. 



former existence, that is in the first eighteen to twenty 

 somites. Mr. Sedgwick, in a foot-note to page 493 (5), seems 

 to doubt his own description as to the origin of a layer of 

 cells situated above and below the somite, dm-ing a particular 

 stage in the development of P. capensis. In Eoperipatns, 

 however, the ventral portion of the ccelomic cavity is ob- 

 literated in exactly the same way as is described by Mr. 

 Sedgwick in the text, with the difference that the obliteration 

 is more extensive, probably owing to the presence of a large 

 quantity of food material in the interior — wanting in P. 

 capensis, — which helps to intensify the pressure brought 

 about by growth. The median coelom of the later stage 

 disappears in the same way as the ventral portion of the 

 earlier stage, that is by the coming together of its two 

 walls. 



Now that the median coelom has been absolutely obli- 

 terated, only the appendicular coelom remains. It was 

 mentioned above that the appendicular outgrowth for a 

 time kept pace with the rudiment of the leg in which it is 

 situated; but this arrangement is not long continued. Its 

 distal end ceases to grow, and a spot on the ventral wall of 

 the appendicular coelom begins to proliferate, resulting in a 

 downward growth which is situated near its proximal end. 

 Its distal end projects into the leg rudiment. This condition 

 is veiy well marked in the appendicular coelom of the third 

 appendage (oral papillee, PI. 7, fig. 12 g'). But this distal 

 projection of the appendicular ccelom, in later stages of the 

 development, seems to be obliterated by the formation in its 

 walls of the rudiments of the leg muscles, which appear to 

 develop to a greater extent in Eoperipatus than in Peri- 

 pat op sis. The downward outgroAvth from the veutral wall 

 of the appendicular coelom soon reaches the ectoderm at 

 the base of the rudimentary leg, and effects a communication 

 with the exterior. The ectodermal indent is at first ex- 

 tremely slight, nearly the whole tube being mesodermal, and 

 throughout the series of changes which give rise to the renal 

 organ, consisting of renal duct and coelom, I have seen 



