86 H. J. FLEURE. 



support of tins homology, but the structure which he takes 

 to be the forecast of tlie Diotocard right kidney is merely a 

 problematic and very transient vestige. The right kidney, on 

 Lankester's view, would become part of the reproductive 

 system, 



Haller thought that the reproductive organs developed a 

 duct which became continuous with the right kidney duct and 

 opened through what was previously the right kidney 

 aperture. The left kidney, he thought, degenerated, but 

 became connected with the right, so that the Monotocard 

 excretory organ was mainly right kidney, but opened through 

 the left kidney's aperture. According to him, only the right 

 kidney retained a pericardial pore. 



Perrier agrees with Haller's conclusions except as regards 

 the pericardial communication, which, he holds, persists only on 

 the left side. He differs also in a point of great importance, 

 for he says that the Monotocard kidney opening is the 

 Diotocard right. His principal contribution to the discussion 

 is the tracing of the fate of the left kidney. This, he found, 

 became the renal gland, consisting of tubules lined by 

 ciliated epithelium, and opening into the kidney cavity. This 

 gland was, he said, typically associated with that ancient 

 moUuscan feature, the "pericardial gland." The conclusions 

 supported in this paper are — 



1. Lankester's viewthat the renal apertureof Monotocardsis 

 the left one of Diotocards. This opposes Perrier's conclusion. 



2. Perrier's and Haller's view that the two kidneys in some 

 Tsenioglossate ancestors came to communicate inter se. 



3. Lankester's and Haller's view that the right kidney 

 opening becomes the genital aperture. This opposes Perrier's 

 conclusion. 



4. Haller's view that the right kidney retains its peri- 

 cardial communication in most Diotocards. This opposes 

 Perrier's conclusion. The evidence adduced is partly new. 



5. Perrier's and Haller's view that the Monotocard kidney 

 is composed of the right kidney of Diotocards, together with 

 the cavity of the left (whose walls form the renal gland). 



