ON DEVEt0r3IENT ETC. OF PlIOKONJ«. ôÔO 



postoral septum {iiicf^.) arc situated. In üg. 47 a, one portion of 

 the peritoneal layer of the stomach wall is als<j represented. Xow 

 we see in the first two hgures of the above series, that the nephi-i- 

 dial canal {iiep c.) which is here imbedded in the somatic la}'ers, 

 lies distinctly below the septum {iiics.). So, in the third ligure 

 the nephi-idial ])ore {ncp.o) is seen as a small pit in the trunk 

 Avail, which is situated considerably Ijclow tlie septum. The in- 

 fraseptal position of the nephridial pores has also been acknowledged 

 l)v Caldwell. '1'1iou<>;1i Mastermax has made no direct state- 

 ment ou this poiut, it may safely be inferred from his figures, 

 that he must have regarded the pores as lying in front of the 

 septum. 



Fig. '31 '( represents a longitudinal section through the middle 

 of the sup]'ase])tal port i ou of the nephridial canal. Here the canal 

 appears as a couiparatively long tube with a narrow lumen; it is 

 invested throughout with a thin mesoblastic ejnthelium. At its 

 upper extremity where the lumen disappears, a certain number of 

 s})indle-shaped excretory cells is found aggregated together. In 

 fig. ül b, which is taken from the same series as fig. 51 a, the 

 canal has wholly disappeared from the section, leaving only a 

 bunch of the excretory cells (e.vo.c.) adhering to the septum {mes.). 

 AU of these spindle-shaped cells have their nuclei in the swollen 

 ends. I have never found either among, or in, the neighbourhood 

 of the cell bunch any perforated excretory cells Ijeariug many 

 processes, — cells which are said to have l)eeu j)resent in the Acli- 

 notrocJia studied by Caldwell. 



Masteemax considers that each Ijonquet of the excretory cells 

 is composed of a cellular mass traversed by a system of minute 

 funnels ; and that these funnels communicate with the main canal 

 of the ncphridium as well as with the collar cavity. But I may 



