64 



At this depth they Hve and thrive at a temperature varying 

 between 4 — 9° C. Zschokke recently (1906 p. 2) states that 

 the Vierwaldstatter See down to its greatest depths is covered 

 with '•'■Rasen und Wäldern'" of Fredericella Bu Plessisi, in 

 other words that even at depths of 214 m. (Halbfass 1903 

 p. 712) with a constant annual temperature of ca. 4 — 5° C. (Am- 

 berg 1904 p. 91 — 93) the fresh-water Bryozoa still occur M. 



These curious deepwater Fredericella which I have also 

 dredged in Lake Geneva are not as is the case with Bryozoa 

 in general attached to other bodies, but like the Pennatuhdes 

 they stick loosely in the mud of the lake bottom. According 

 to Forel they have the power of moving and when kept in 

 glass vessels are said to be able to rise out of the mud at 

 the bottom and at will to fasten themselves in the same. Da- 

 venport mentions (1904 p. 213) that Paludicella Ehrenbergii 

 and Fredericella sultana have been determined in catches from 

 Lake Michigan at depths of 23 — 36 m. For my own part [ 

 have often during several years taken shells of mussels at 11 

 — 15 m. with fixed statoblasts of Plumatella attached to them 

 and besides at one dredging in Furesø, estimated at 20 m., I 

 got a colony of Cristatella. 



Further, it has been established that fresh-water Bryozoa 

 inhabit lakes almost verging on the snow region. The species 

 which according to Zschokke (1900 p. 115) occur in mountain 

 lakes are Fredericella sultana^ Plumatella repens and Cristalla 

 nmcedo^ of which Cristatella has been found at the greatest 

 height (2293 m.). From lakes in the Engadin valley at 1825 m. 

 above sea level Zschokke reports Fredericella as occuring 

 abundantly even below the icecover of the lakes. 



Besides these examples furnished by the fauna of our 

 own day we may also point to the Bryozoa of past epochs 

 for evidence which unmistakably shows that these organisms 



The same species has quite recently also been found in the abyssal 

 region of lake d'Annecy (Marc le Roux 1907 p. 267). 



