194 
EDWIN S. OnODRICH. 
altliougli sometimes the epithelium seems to stretch over the 
base of the solenocyte tubes for a considerable wny. The 
coelomic epithelium is not continuous with the wall of the 
canal at the tip of the diverticula, but often can be seen in 
sections to end with a free and jagged edge. Over the region 
where the solenocytes occur there is a gap in the coelomic 
epithelium, so that coelomic fluid freely bathes the solenocyte 
tubes (figs. 2, 3). That the space in which lie these tubes, 
and even the deep pockets described above (p. 193), commu- 
nicate with the coelom is evident in specimens injected with 
Indian ink. 
Since no epithelium covers the solenocytes their true rela- 
tion to the coelom cannot be made out for certain in the 
adult. Without going into the question of their develop- 
ment in this paper, I may say that a careful examination of 
M. Legros’s excellent preparations has convinced me that in 
the very earliest stages of its development the whole rudi- 
ment of the nephridium and solenocytes lies enclosed betw'een 
the coelomic epithelium and the atrial wall. There is nothing 
unusual in the solenocytes coming into secondary contact 
with the coelomic fluid. We know that in the Actinotrocha 
larva the nephridium pierces the wall of the preseptal 
hmmocoel, and the solenocytes project freely in the blood 
(8). In many Polychmtes also the nephridium passes tlu’ough 
the coelomic epithelium and the solenocytes lie naked in the 
coelomic fluid (6) . 
To sum up the chief points in this contribution : — The 
careful examination of the nephridia in sections and in the 
living state shows that they have no internal opening. The 
tubes of the solenocytes pierce the wall of the nephridia! 
canal, and open into its lumen. The flagellum passes down 
the tube into the lumen. The solenocytes are attached to 
the wall of the bloodvessels, which expand in this region, and 
may surround the canal. Both the bloodvessels and the 
nephridial canal are covered by the coelomic epithelium, 
being situated between it and the atrial wall. Over that 
region which is occupied by the solenocytes there is a gap in 
