90 



midline into the epibranchial cavity, undGi* the vi::coral 

 Can^lion. The efferent duct is lined by coluximar, vacuo- 

 lated and apparently secretory cells, which are not cil- 

 iated except at the anterior end, and also neai* the exter- 

 nal opening. 



Venous blood from the posterior end of the body re- 

 turns by an efferent renal vein (figs. 33,34, a.r.v.)which 

 runs in the mantle, and on a level v/ith the posterior ends 

 of the kidney duct, enters the peri-ronal blood spaces 

 (figs. 29-51). After bathing the kidneys, it enters the 

 general venous circulation. 



Pelseneer, who, it seems, observed onlj'' the poste- 

 rior ends of the kidney ducts , described them as much pouch- 

 ed. In properly prepared specimens of X. fimbriata, I 

 find that, while the body of the kidney is much pouched, 

 the ducts form straight cylindrical tubes. Preserved 

 "Ship-worms" are almost always very greatly shrxxnken, and 

 I am inclined to believe that this fact accounts for Pelse- 

 neer's results. Also, contrary to the statements in text- 

 books (Lang) , I find that the two kidneys of X. fimbriata 

 do not communicate with eacli other, as they do in Pholas 

 and other foxras. 



