RELATIONS OF KIDNEYS IN HALIOTIS TITBERCULATA. 81 



that of Perriei" and Erlanger. The wall of the sac is very- 

 thin, especially where it overlies the branchial vein. AVhen 

 it abuts on the pericardia ui it is also thin-walled over a part 

 of the area, but the remainder is thickened into a mass of 

 lymphatic tissue. There are vascular connections taking 

 blood to the efferent branchial vein and thus to the auricle 

 direct. Perhaps some one of these is what has been taken 

 for a pericardial communication of the papillated sac. 



To sum up, therefore, I think that Haliotis tuberculata 

 has two separate kidneys right and left of the pericardium, 

 opening externally by separate apertures (1 and 2). I find, 

 also, that the gonaduct opens into the right kidney, which is 

 the functional excretory organ, while the left kidney is partly 

 degenerating into lymphatic tissue, and is becoming con- 

 nected with the efferent branchial vein by direct blood- 

 channels. So far my results agree with Perrier's. I find, 

 further, in opposition to Perrier, and in agreement with 

 Haller, that the right or functional kidney communicates with 

 the pericardium (via 5), while the left one does not. The 

 evidence adduced is, in part, of a different nature from 

 that brought forward by the authors mentioned. 



The foregoing results, if correct, lessen the divergence 

 hitherto supposed to exist in this respect between Haliotis 

 and Patella. The limpet has two kidneys right (7 r, fig. 3) 

 and left of the rectum. The right kidney is very extensive, 

 and performs most of the excretory work; it has several lobes, 

 including a subrectal one (s. p., l.), which abuts on the wall of 

 the pericardium. It serves as an exit channel for the repro- 

 ductive elements, but evidence I have collected recently 

 seems to hint at liberation of ova, at any rate, by rupture 

 as well. This matter, however, needs further investiga- 

 tion. 



The small left kidney is situated between the rectum and 

 the pericardium, its circulatory system connects it intimately 

 with the auricle. It is not shown in the diagram. 



The right kidney communicates with the pericardium (8), 

 the opening (2) being in the floor of the kidney's subrectal 



VOL. 46, PART 1. — NEW SERIES. F 



