Videnskabelige meddelelser

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Videnskabelige meddelelser

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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. Geologicai 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 connected

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 Riigen into land). Obviously Planarui nipina

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 Plannria 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-

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