65 



must be quite able to exist at a much lower temperature than 

 our present knowledge of their geographical distribution would 

 seem to warrant. In samples of chitin and silicious fragments 

 from Scandinavian peat bogs kindly sent me some years ago 

 by Gunnar Anderson I was able (1896 p. 51) to determine 

 Cristatella statoblasts so early as in the Dryas-layers; Plmna- 

 tella did not occur until the pine period. Since then Crista- 

 tella as well as Plumatella statoblasts have been reported by 

 several observers as well as by myself in the quartär layers of 

 Denmark, Sweden, Norway, Finland and North Germany. As I 

 thought it unnecessary to mention here the numerous places of 

 discovry, I applied to the intimate connoisseur of the fauna 

 and flora of the Danish peat-bogs, N. Hartz, for some general 

 information as to the occurrence of Bryozoa statoblasts in our 

 peat-layers. According to Hartz the statoblasts of the above- 

 mentioned Bryozoa are found throughout all the several layers, 

 the Cristatella occurring most commonly, whereas in the Dryas- 

 layers the Plumatella are more rare. 



Consequently it cannot be denied that, whether we con- 

 sider the occurrence of the fresh-water Бгг /oøoa of the present 

 time or call to mind their vertical distribution during past ages, 

 in both cases it seems extraordinary that now-a-days the Bry- 

 ozoa should cease at so great a distance from the polar circle 

 as has hitherto been supposed to be the case. If these orga- 

 nisms have been able to exist under the natural-conditions of 

 the Dryas-period and if still able to liwe at the low tempera- 

 tures prevailing at the bottom of the Viervvaldstattersee as also 

 in Alpine lakes situated near the snow-region, we should be 

 justified in supposing that, although the natural conditions ob- 

 taining in countris beyond the arctic circle at the present day 

 do not admit of a direct comparison with the conditions pre- 

 vailing at the period where the Dryas layers were deposited in 

 our own latitudes, that the northern limit of these forms at 

 present would extend farther to the north. 



