600 DR. R. V. ERLANGER. 
the four Neapolitan species of Fissurella, and have abso- 
lutely satisfied myself that no such thing exists. The spe- 
cimens of Fissurella had been most carefully preserved and 
stained, the sections extended without a break through the 
whole length of the pericardium. Fig. 16 shows the point 
in which the right kidney runs into the nipple immediately on 
the ventral and right side of the pericardium. In this section, 
as in all others, the brown epithelium of the right kidney is 
seen to extend over the whole inner surface of the nephridium, 
without any interruption whatever. 
Perrier, in his answer to a letter which I wrote to him on 
the subject, stated that he had made an injection into the peri- 
cardium of Fiss. costaria, and that the coloured fluid had 
penetrated into the right kidney. This can be easily accounted 
for. The beginning of the right kidney lies immediately below 
the pericardium, and its cavity is only separated from that of 
the pericardium by the epithelium of the kidney, the exceed- 
ingly thin tunica propria of this gland, and the delicate wall 
of the pericardium. When an injection is forced into the peri- 
cardium under a high pressure—with asyringe, for instance— 
the liquid bursts through the wall of the pericardium and 
kidney at the point just mentioned. I have myself made the 
experiment. When using the method described in this paper 
such a thing never happened; when, on the contrary, I used 
a syringe, I very often found the injection in one or the other 
kidney, sometimes in both, as they both come into the closest 
proximity with the wall of the pericardium. This place in 
both kidneys probably corresponds to the spot in which the 
nephridium was constricted off from the pericardium or celom, 
and is very likely homologous to an abortive funnel in both 
cases. 
I have been quite unable to find any trace of a reno-peri- 
cardiac canal like the one figured by Perrier (238) in pl. i, 
fig. 3, of his paper. The above-named gentleman, at my 
special request, has very courteously promised to look over 
his preparations, giving special attention to this point, but I 
have not yet received information as to the result. 
