EELATrONS OF KIDNKVS IN HALlO'l'IS TTTHI'^RCITLATA. 83 



kidney is, practically, an accessory genital organ in posse. 

 The external opening (2) of the right kidney is evidently 

 becoming a genital pore. 



Trochus and Turbo vary very much in this respect, but in 

 some species the " anterior lobe " is very sharply marked off 

 from the rest of the kidney. There is the same conflict of 

 opinion between Perrier and Haller about the reno-pericardial 

 funnels in Trochus as in Haliotis, and Haller finds also an 

 interrenal communication in Trochus gibberosus. With 

 regard to these reno-pericardial funnels it is noteworthy that 

 in all Tfenioglossa, even in the most primitive (figs. 6 and 8), 

 and in Nerita there is a well-marked communication between 

 kidney and pericardium on the right side of the latter — a 

 fact which strongly supports the view here put forward, that 

 the right reno-pericardial pore is retained, as a rule, in the 

 Ehipidoglossa. 



If the right excretory pore (2) becomes monopolised by the 

 genital system, the functional kidney must find an exit for its 

 excretory products ; and it seems probable that this exit is 

 through the external opening (1) of the left kidney, which 

 would thus be the homologue of the Monotocard excretory 

 aperture. The probability of this is increased by the fact 

 that in no Monotocards have traces of a pore or sac been 

 found to the left of the kidney opening. This view, however, 

 entails the further supposition that the right kidney, or 

 rather its posterior part, comes to communicate with the left 

 kidney, and Haller claims, as was mentioned above, that such 

 a communication already exists in Haliotis glabra and 

 Trochus gibberosus. Perrier contradicts Haller, though 

 he, too, supposes that the two kidneys come to communicate; 

 he, however, almost certainly errs in stating that the Monoto- 

 card kidney opening is the right one (2) of Diotocards, for 

 this statement raises a serious difficulty as to the homology 

 of the genital opening. 



Bouvier found such an interrenal communication in Am- 

 pullaria (5), and Perrier justifiably uses this observation in 

 support of his views above mentioned. He further supports 



