DISTRIBUTION IN TIME AND SPACE 245
the north.
The glaciers that extended downwards from
Scandinavia and
North Rtmsia over Mid-Europe 'and
England as far as Buckinghamshire made a.Clean swéep of
'
the earlier inhabitants of the lakes and streams. The same
’
thing happened in North America, Where the Ice—cover.
extended some 5° still farther
A 'nèwpoiaulaori
then arose. and Regan shows how the'mosttcharacteriStic"
freshwater forms of
Britain, the Chars (SalVeliüs)
and VVhitesh (Coregonus), belong to a -m0re northerly
fauna.
They“ were left behind in isolated lakes as the Ice—ÿ
'
cover retreated and have. adapted themselves so 'wellto the
'
varied coditi0‘s that almost every lake has its own peculiar .
race'ùr species—. They are' now frèshwatef— shes, but their
n0rtherh relatives spend some par-‘t of their time in the sea.
'
These are
“the only species peculiar’to the” British fresh—
.
water fauna. 'The Char also occurs in isôlatedlakes of
_
Scandinavie£ and the Alps, but not in Germany. Coregonùs'
is represented by other distinct
,
forms in the countries
round the Baltic, but the main types. of the family live as
ahadromous sheé in the ArCtiC Ocean and'rivers of”Siberia.
'
'
In addition to_'thesereliCts of the Glacial periods, the,
also contain a Considerable number of true
freshwater
'
species-, isucÏh, 1asÇ the…,Perch, _Pike_,. Carps, and, "
Loâches
on the Continent of
most of them even in
'
'
that of thetwenty—two sp‘eCieS mentioned“ by 'Reganfonly'one _
occurs in. the Iberian Peninsula. — These
forms
have thus come from the east and have entered the :BritiSh
'
.
waters from theRhine region. when South Britain Was Still
,
-'
—
With the Continent.
Once more, therefore;the
,
"
=œthemçwatas have been stocked from the east. These
'
'
"shes
entered by way of the Humber and
T rëht;”'à'rid Regan is able to show that their
‘
the 7wèst',"'sôutli'gfaiid
has bee'nvety graduafl. '
re“npr the twenty-tWo species ,Ç '- ' ‘
,
'
Even
the relations ÏWithf‘Nor-th
Americzi.
6o)ai1d 'thëÏ—BuÏrbot
there in the
Lakes “and-northwafds; aswe‘ll‘as several
'
the north.
The glaciers that extended downwards from
Scandinavia and
North Rtmsia over Mid-Europe 'and
England as far as Buckinghamshire made a.Clean swéep of
'
the earlier inhabitants of the lakes and streams. The same
’
thing happened in North America, Where the Ice—cover.
extended some 5° still farther
A 'nèwpoiaulaori
then arose. and Regan shows how the'mosttcharacteriStic"
freshwater forms of
Britain, the Chars (SalVeliüs)
and VVhitesh (Coregonus), belong to a -m0re northerly
fauna.
They“ were left behind in isolated lakes as the Ice—ÿ
'
cover retreated and have. adapted themselves so 'wellto the
'
varied coditi0‘s that almost every lake has its own peculiar .
race'ùr species—. They are' now frèshwatef— shes, but their
n0rtherh relatives spend some par-‘t of their time in the sea.
'
These are
“the only species peculiar’to the” British fresh—
.
water fauna. 'The Char also occurs in isôlatedlakes of
_
Scandinavie£ and the Alps, but not in Germany. Coregonùs'
is represented by other distinct
,
forms in the countries
round the Baltic, but the main types. of the family live as
ahadromous sheé in the ArCtiC Ocean and'rivers of”Siberia.
'
'
In addition to_'thesereliCts of the Glacial periods, the,
also contain a Considerable number of true
freshwater
'
species-, isucÏh, 1asÇ the…,Perch, _Pike_,. Carps, and, "
Loâches
on the Continent of
most of them even in
'
'
that of thetwenty—two sp‘eCieS mentioned“ by 'Reganfonly'one _
occurs in. the Iberian Peninsula. — These
forms
have thus come from the east and have entered the :BritiSh
'
.
waters from theRhine region. when South Britain Was Still
,
-'
—
With the Continent.
Once more, therefore;the
,
"
=œthemçwatas have been stocked from the east. These
'
'
"shes
entered by way of the Humber and
T rëht;”'à'rid Regan is able to show that their
‘
the 7wèst',"'sôutli'gfaiid
has bee'nvety graduafl. '
re“npr the twenty-tWo species ,Ç '- ' ‘
,
'
Even
the relations ÏWithf‘Nor-th
Americzi.
6o)ai1d 'thëÏ—BuÏrbot
there in the
Lakes “and-northwafds; aswe‘ll‘as several
'