DELATIONS OF KIDNRYS IN HALIOTIS TUBEROULATA. 89 



between the anus and the genital aperture (fig. 15), but this 

 peculiarity may be connected with the development of a ureter. 



APPENDIX. 



Since the above paper was written I have had an oppor- 

 tunity of seeing Pelseneer's recent publication ' Les 

 Mollusques archaiques/ and as he touches here and 

 there the questions of kidney homologies, a short discussion 

 of the work of this eminent scientist will add to the com- 

 pleteness of this little paper. 



The chief new facts which he brings forward all support 

 the conclusions I have ventured to set forth. 



1. He finds that, in the Trochidas, the right kidney has a 

 communication with the pericardium, and, as I have found 

 the same feature in Haliotis, arguments for the degeneracy 

 of the right kidney of Rhipidoglossa, based on the absence of 

 its pericardial communication, are definitely demolished. 

 Pelseneer also finds the distinction between anterior and 

 posterior regions of the right kidney of Trochus Avhich has 

 been mentioned in this paper as regards Haliotis. 



2. He finds tliat Haller's interpretation of the kidneys of 

 Cemoria was based upon errors of observation. As he has 

 carefully examined specimens both from the source to which 

 Haller had recourse (the Vettor Pisani collection) and 

 from the White Sea, there seems to be little doubt that 

 Pelseneer is right. If so, Cemoria, in its excretory and 

 genital systems, resembles the typical Fissurellid. Its right 

 kidney is of enormous extent, while the left is quite tiny, 

 and only the right gonad is found. 



This result is of great interest, as it is now possible to say 

 that in all known Rhipidoglossa the left kidney is either ex- 

 tremely reduced or has undergone a transformation into 

 a "papillary sac," an alteration which has profoundly 

 affected its minute structure and its circulatory arrange- 

 ments. It is therefore still more difficult than before to 



