RECENT FRESHWATER INVESTIGATIONS 323 



apparently in strong contrast to that of a neighboring basin. 



In an earlier paper (94) Zschokke presented the results of 

 studies on lakes in the Jura showing a typical mountain char- 

 acter. Previously de Guerne et Richard (93) had investigated 

 the limnetic fauna in the same region and (94) in the Pyrenees. 

 In the Cottian Alps Blanchard et Richard (97) found similar 

 fauna! conditions. Here also Blanc, Pitard, Imhof (93), 

 Pugnat (97). The varying fauna in adjacent basins is explained 

 by the last mentioned author on the ground of variation in the ex- 

 posure and illumination of the water. Studer (93) attributed 

 the poverty of the limnofauna in the lake of Champex to the 

 excessive illumination of the shallow water in the absence of 

 shore and bottom plants. Imhof (95a) investigated the hori- 

 zontal and vertical distribution of the aquatic mollusea in the 

 Alps. They are more numerous in the territory of the Rhone 

 and the Po, and manifest in small and in elevated lakes a rapid 

 reduction in number. On the southern slope of the Alps Fuhr- 

 mann (95) finds the fauna of the elevated lakes similar, though 

 somewhat richer. In the Julian Alps Lorenzi (97) finds a cos- 

 mopolitan fauna in which the plankton consists of tychopelagic 

 forms alone. In the Riesengebirge according to Zacharias 

 (96g, 98c) the limnetic fauna is scanty but similar to that of the 

 Rhaeticon lakes studied by Zschokke. The 3pecies present are 

 typical cold water forms. The same poverty and cosmopolitan 

 cast in the fauna is reported by Fric and Vavra (97) who at- 

 tribute the scanty shore and bottom fauna to the lack of vege- 

 tation. The disappearance of certain elements in the fauna 

 can be traced definitely to the introduction of game fish. In 

 the Tatra lakes, Galicia, Wierzejski (95) found typical Alpine 

 conditions in the poverty of species in the abundance of cosmo- 

 politan forms and in the contrast in proximate basins of equal 

 altitude. The lakes show, however, as Daday (97) remarks, 

 notable richness of fauna even up to an altitude of 2,000 m. 

 Here also Richard (98a, 96c). In Syria Barrois (94) found an 

 unusually rich limnetic fauna of cosmopolitan Entomostraca 

 and Rotatoria. The Sea of Tiberius, though strongly saline, 

 has a pure lacustrine fauna. 



