324 EDWIN S. GOODRICH. 



Jhering ten years later, in an important paper on the kidneys 

 of molluscs, states that he was unable to find a reno-pericardial 

 communication : " Die Pericardialoffnung sah ich nicht" (1877, 

 Jhering). In 1881 Lankester and Bourne together reinves- 

 tigated the question, and described the canal thus : — " Its 

 presence can be demonstrated both by injections which pass 

 from the pericardium sometimes into the right, sometimes 

 into the left renal sac, and by dissection. The orifice leads 

 directly into a narrow subanal tract of the further or 

 right renal sac, and not directly into the left or small renal 

 sac " (1881, Lankester). It will be seen that, curiously enough, 

 although the presence of the canal previously described as 

 leading into the left kidney is not actually denied, yet the author 

 seems not to be convinced of its existence. Shortly after, Mr. 

 J. T. Cunningham undertook the study of these canals by 

 means of series of sections (1883, Cunningham). In this paper, 

 to the details of which we shall refer later on, two pericardial 

 canals are described leading into the small left and large right 

 kidneys respectively in Patella coerulea. The fact that only 

 a diagram of the canals is given, and that Cunningham made 

 use chiefly of injected material, perhaps contributed to weaken 

 the evidence brought forward. The main facts were, however, 

 confirmed by Mr. Harvey Gibson in his studies on the anatomy 

 of Patella vulgata (1887, Gibson). An important memoir on 

 the kidneys of the Prosobranchs was brought out by M. Remy 

 Perrier in 1889 ; in this work the author states that although 

 he made use of sections, and found the right reno-pericardial 

 canal, yet he was unable to find a canal opening into the left 

 kidney : " Je n'ai pu retrouver la communication du pericarde 

 avec le rein gauche." Perrier concludes that the right kidney 

 alone communicates with the pericardium (1889, Perrier). 



We now come to the most sensational cliapter in our story. 

 In 1892 Dr. R. von Erlanger published an elaborate work on 

 the 'Paired Nephridia of Prosobranchs' (1892, Erlanger), in 

 which he positively denied the existence of any reno-pericardial 

 duct in Patella. The author, criticising the injection method, 

 maintained that previous observers had been misled by the 



