14 WALTER K. FISHER, 



Its ultimate branches are essentially tiny blind ducts or lobules, the 

 lumen of which is surrounded by the liver cells. 



From a joining of these, larger spaces or sinuses are formed, 

 till finally the main collecting canals result, which uniting into one, 

 open into the stomach at its anterior end. The liver cells line the 

 duct to its union with the stomach. 



Excretory System. 



The nephridia. The nephridia of the Docoglossa have given 

 rise to considerable controversy, not only respecting their extent but 

 also regarding the so-called reno-pericardial canals. The Acmaeidce 

 , have more especially been the subject of debate in recent years. As 

 to the extent of the kidneys there can be no possible doubt, for in 

 Acmaea mitra, A. spectrum, A. pelta, A. patina, A. scabra and A. per- 

 sona, as well as in Lottia gigantea essentially the same relative po- 

 sitions are held by the right and left nephridia, and the disproportion 

 in the size of the two also obtains in all these species. Consequently 

 it is with considerable perplexity that one must regard the remarkable 

 results of Bela Haller's work on Lottia viridula 1 ). In fig. 15 of his 

 "Studien iiber Docoglosse und Rhipidoglosse Prosobranchier" the right 

 nephridium is represented as made up of two relatively small sacs joined 

 by a narrow neck. One of these sacs opens to the exterior, the other 

 communicates by a remarkable passage with the pericardium. The 

 animal which possesses such a nephridium has no place in the Ac- 

 maeidce. As suggested by Willcox (in : Zool. Anz., Jg. 1901, p. 623) 

 Haller has probably taken only a portion of the right kidney, calling 

 the rest coelom. Even with this explanation, there are other incon- 

 gruities in the figure which are not explained, as, for instance the 

 wide mouth, into the right kidney, of the reno-pericardial duct. This 

 does not accord with the condition found in every Acmaeid which has 

 so far been examined by other observers, nor with the structure in 

 the Patellidae. As a matter of fact the opening is excessively small. 



When the shell is removed from a yet unhardened Lottia gigantea 

 the extent of the large right nephridium is easily observed through 

 the dorsal body wall, by reason of a dark green excretion which 

 covers the renal epithelium. The nephridium is thus seen (Fig. 20 

 B.K, in blue) to encircle almost the whole visceral mass from right 



1) Studien iiber Docoglosse und Rhipidoglosse Prosobranchier, 

 Leipzig 1894. 



