608 DR. Rk. V. ERLANGER. 
kidneys further supports my own view. The lamellar organ 
closely resembles the kidney in the embryo of Bythinia, as 
described by myself (9), while the size of the left kidney and 
the simplicity of its structure strongly remind one of the 
right renal organ in Diotocards and Heterocards. 
I must now beg the reader to refer to my fig. 24 of Tec- 
tura species which shows that the left kidney (the small 
one) lies quite anteriorly to the large right one, a fact which 
might explain the position and homologies of the renal organs 
of Ampullaria, further supporting my own view on the 
subject. 
Bouvier, whose abilities as an anatomist I value most 
highly, has only examined specimens of Ampullaria preserved 
in spirit, and exclusively made use of the method of dissec- 
tion. I must venture, therefore, on technical grounds, to 
question some of his statements. It seems highly improbable 
to me that the lamellar renal organ should have no communi- 
cation with the pericardium, whilst the kidney of Bythinia, 
which is closely similar to it in shape and texture, clearly 
shows a well-defined reno-pericardiac duct. This point, and 
the communication of the two renal organs, ought certainly to 
be reinvestigated in well-preserved specimens by the method 
of sections. Bouvier has shown and stated that the organi- 
sation of Ampullaria closely resembles that of Paludina. 
Ampuilaria (says Bouvier) is a large Paludina, which by 
adaptation to a new mode of life has acquired a lung. The 
results obtained by the study of the development of Palu- 
dina may therefore safely be applied to Ampullaria, all the 
more as the species described by Bouvier is leiotropic like 
Paludina. I consequently am quite convinced that the 
lamellar kidney of Ampullaria is homologous with the 
actual left kidney of Paludina, the vascular sac in 
Ampullaria to the rudimentary right kidney in Paludina. 
Before taking leave of the kidneys of Prosobranchs, I 
must yet mention the curious organ in Dolium described 
by P. Schiemenz (26) under the name of anal kidney (Af- 
terniere). This organ consists of two brown glandular 
