588 DR. R. V. ERLANGER. 
this fact with the statement that the right kidney of Zygo- 
branchs and Cyclobranchs serves as a duct for the sexual 
products, I was led to the conclusion that the actual right 
kidney disappears or becomes highly modified, while its duct is 
converted into that of the genital gland. 
Reading the works on the comparative anatomy of Gastro- 
pods, I was struck by the contradictory statements about the 
reno-pericardiac duct in Zygobranchs, Cyclobranchs, and 
Prosobranchs. Ray Lankester, in his first paper on Patella 
(18), stated that he found a communication between the actual 
left kidney of Patella and the pericardium. In a second 
paper he only describes a right reno-pericardiac duct in the 
same species. V. Jhering (16) could not find any communi- 
cation between either kidney and the pericardium in Fissurella 
and Patella, at least, as he says, with any certainty, while he 
was able to find it in Haliotis. Bontan (2) failed to see the 
left kidney in Fissurella, and could not find a reno-peri- 
cardiac canal in the right kidney. B. Haller (18) describes a 
right reno-pericardiac duct in Fissurella. Wegmann does 
not mention any communication for either kidney and the 
pericardium in Patella (28), although he found a left reno- 
pericardiac duct in Haliotis (27), where the right kiduey has 
no opening into the pericardium. Cunningham (7), at Ray 
Lankester’s suggestion, re-examined Patella, and found a 
reno-pericardiac duct for both kidneys. The last anatomist 
who studied the kidneys of a great number of Prosobranchs, R. 
Perrier (23), describes a right reno-pericardiac duct in 
Fissurella and Patella, but could not find a left one in 
either of these two species. On the other hand, he found only 
a left pericardiac duct in Haliotis, Trochus, and Turbo. 
The conclusion to be drawn from this historical résumé is, 
I think, that the subject was well worth a new investigation. 
I accordingly have studied five different species of Fissurella, 
Emarginula, Puncturella (closely related to Rimula), 
one species of Patella, a Tectura, one species of Haliotis, 
one of Trochus, and a Turbo. My results, as the sequel 
will show, are somewhat surprising as regards Fissurella and 
