02 BICHARD EVANS. 



From the posterior inner corner of the renal portion a fine 

 canal passes to the exterior, its external opening being 

 situated immediately in front of the rudiment of the jaw and 

 on the inner side of the forecast of the lip (PI. 7, figs. 12 d 

 and 12 e). It is only fair to point out that this communica- 

 tion with the exterior was discovered many years ago by 

 Miss Sheldon in P. novte-zealandise (6), and that the 

 nephridium of the first somite had been seen and identified 

 by Mr. Sedgwick in P. capensis (6). Consequently, the 

 somite under consideration was clearly shown to have the 

 same morphological value as any one of the succeeding 

 somites. Owing to the great increase in size of the cephalic 

 ganglia and first pair of ventral organs, the communication 

 of the first somite with the exterior soon becomes obliterated, 

 and the two portions into which the somite is divided be- 

 come much reduced in size and finally disappear. Fig. 22 a, 

 som}, on PI. 9 shows the remnants of the first pair of somites 

 as small spaces situated above the brain and in front of the 

 eye. 



(3) The Development and Disappearance of the 

 Second Somite (sovi."). 



The early stages in the history of the second somite have 

 been noticed in describing the first and second, embryos, and 

 are illustrated in figs. 10 c and 10 d on PI. 6, in which it 

 is shown that the somite in question passes above the first 

 one, situated in front of it, and below the third^ which suc- 

 ceeds it. 



Fig. 11 /> on PI. 7 shows the somite under considera- 

 tion much compressed, and displays a tendency on the part 

 of its walls to come together, and consequently to obliterate 

 the coelom. 



Dorso-ventrnlly, however, the somite presents a consider- 

 able extension. The same figure also shows the latei-al out- 

 growth of the coelom, which extends the whole length of the 

 rudimentary second appendage. The outgrowth in question 

 is a ti-ue appendicular coelom, on the vontrnl wall of which 



