ON THE HENO-PERIOARDIAL CANALS IN PATELLA. 327 



Comparing this description with that given by previous 

 observers, it may be remarked that in the main my results 

 agree with and confirm those of Cunningham ; yet neither he 

 nor Gibson appears to have seen the well-marked funnels. 

 On the other hand, like Gibson, I am unable to find the 

 " triangular piece of tissue " described by Cunningham as 

 forming "a sort of valve ^' over the opening. It is difficult, 

 indeed, to see how such a flap would act in connection with the 

 papilla. Haller describes a ciliated funnel at the right reno- 

 pericardial aperture without figuring a section through it; but 

 he further states that the canal itself is lined with high columnar 

 cells. This is certainly not the case in the species I have inves- 

 tigated, and I cannot help thinking that he may have mistaken 

 in this instance a branch of the ramifying kidney for the reno- 

 pericardial canal. Both the kidneys give off numerous branches 

 lined with epithelium similar to that of the main renal 

 chambers. 



In the four series of sections of Patella vulgata examined 

 I have always found the two reno-pericardial canals present, 

 and well developed. In Patella coerulea I have observed 

 two canals of essentially similar structure, — in fact, the 

 description given above applies equally well to either species. 



Summary. 



In the foregoing pages it has been shown that in Patella 

 vulgata and coerulea there are two reno-pericardial canals, 

 opening by means of projecting ciliated funnels^ from the 

 pericardium into the right and left kidneys respectively. 



List of References. 



1883. Cunningham, J. T.— "The Renal Organs of Patella," ' Quart. Journ. 



Micros. Sci.,' vol. xxiii, 1883. 

 1892. Erlanger, R. von. — "On the Paired Nephridia of Prosobranchs," 



' Quart. Journ. Micros. Sci.,' vol. xxxiii, 1892. 



Similar but better developed structures are found at the mouth of the 

 reno-pericardial canals of Chiton and other molluscs. 



