RELATIONS OF KIDNEYS IN HALIOTIS TUBEROULATA. 87 



This I would slightly modify by stating that it is tlie posterior 

 part of the Diotocard right kidney which seems to me to 

 become the functional part of the Monotocard kidney. 



6. I would also suggest, in a very tentative fashion^ that 

 perhaps the forecast of tlie accessory reproductive organ^ 

 which becomes penis or brood pouch in the Monotocards, 

 was originally a dilatation on the reproductive duct. Perhaps 

 even an earlier condition of this organ is what has been called 

 the anterior lobe in the Diotocard kidney. 



After outlining these conclusions I saw Mr. Martin Wood- 

 ward's paper on Pleurotomaria Beyrichii. In a short 

 discussion at the end of his paper he speaks in favour of con- 

 clusions identical with Nos. 1, 2,3, and 5 above, but from his 

 observations on Pleurotomaria he sides with Perrier as 

 regards 4. Even, however, had I not found a reno-pericardial 

 communication for the right kidney in Haliotis, I think there 

 would still have been a balance of evidence from Fissurella, 

 PateHa, perhaps from Trochus, and especially from Nerita, 

 Nassopsis, Paludiua, etc., in favour of the view that the 

 Monotocard reno-pericardial opening is that of the Diotocard 

 right side. 



More work on the Trochidge and Neritidte is necessary for 

 any further advance towards certainty in the matters above 

 discussed, but it is interesting to note that Nerita has a 

 single kidney with a well-marked pericardial opening on the 

 right side of the pericardium, while the external aperture is 

 to the left of the rectum. The genital system, described by 

 Haller, is quite separate from the excretory organ, and lies to 

 the right of it. The kidney has no anterior lobe correspond- 

 ing to that of Haliotis. The chief interest of the Trochidte, etc., 

 arises from the theory put forward by Perrier, Bouvier, and 

 others that these forms are very near the ancestral stock of 

 the Monotocards. Mr. Woodward, however, does not seem 

 to share this opinion. 



It has been a difficulty to represent, in diagrams ] — 10 the 

 true relations of the anal, excretory, and genital openings, 

 and Professor Davis therefore suggested to me the addition 



