72 
land and 90 km from Rugen, the nearest locality where relics are 
found, is of great interest. An immigration in recent time is out 
of the question, and even in late-glacial times it can scarcely have 
spread across the sea. Geological facts prove that Bornholm, at 
some epoch after the latest glaciation, has been situated consider- 
ably higher than it is now-a-days; undoubtedly the island was con- 
nected with North Germany (an upheaval of little more than 20 m 
would be sufficient to change the sea-bottom between Bornholm 
and the district E. of Rugen into land). Obviously Planaria alpina 
has immigrated to Bornholm during this time. 
By the Danish geologists (Milthers and others) this land- 
connection is assigned to the Ancylus epoch. According to recent 
researches the improvement of climate advanced, however, very 
rapidly; already early in the Ancylus period the climate was at 
least as warm as it is to-day. Even during the latest part of the 
late-glacial period (De Geers fini-glacial epoch) the climate was, 
to judge from many facts, so warm that Planaria alpina , when 
existing as far from the ice-border as in the latitudes of Bornholm, 
certainly could no longer spread into new regions. The immigra¬ 
tion must, therefore, date from an earlier epoch. 
Geological facts 'do not contradict this assumption. On the con- 
trary, it is well known that in Southern Scandinavia an intensive 
* 
upheaval of land began very soonly after the retreat of the ice- 
border. Munthe has come to the conclusion that in the latest 
part of the late-glacial period the recession of the sea perhaps pro- 
ceeded to such an extent that even that time Gottland was con- 
nected with North Germany. It may be assumed even more easily 
that Bornholm was connected with the continent at a still ear¬ 
lier date. 
Planaria alpina has consequently immigrated to Bornholm from 
the south by means of a connection with North Germany, presum- 
ably very early after the retreat of the ice-border. 
Some remarks upon the immigration of the land-fauna 
to Bornholm. 
In the second part of the paper the immigration of the land¬ 
fauna to Bornholm is discussed, in particular the immigration of 
animals that can cross the sea only by more or less rare and ex- 
