34.
THE BIOLOGY OF FISHES
we come to a different set of phenomena. How soon they
choose their own way is uncertain, but we cannot‘regard
.
them any longer as quite helplessly drifting with the currents.
And they' are now able, by swimming, to overcome the
'
difference in specic density between themselves and the
surrounding water—to some extent. Many of the young
larvæ swim actively up to the surface, but when they cease
_
to Swim, they gradually sink. They must keep on the move
_
to remain on the surface.
We may say that on the whole
-
they remain in the body of water surrounding them and are
thus carried along by the currents, but their own activity
in cho'osing the body=of water has to be taken into account.
'
_
Fore‘*æmple, the-fry of the springHerring make their way
_
;froriithe'bottomhp-to;the-Surface and take about three weeks
their ascent ; the y,o_fthe autumn Herring, on the other
.
coihe;upto— the Surface. They remain near
the;Ïwi_nter.… In ,neither case “can
;we; explain the phenomena as«Wholly; due to the
being
'
to particular
-
This is also seen clearly in thecas'e of the Plaice. Wïlienï :
—,
'
_
sinkdown to the bottom, they ought to remain there,
whatever maybe the depth. Yet they only occur near the
_
shore, right on the beach. Redeke, it is true, found some
one—year old Plaice some distance from the coast off Holland ;
.,
but the water there is very shallow and the specimens may
j
out from the shore.
It may be, of course,
thatthereareunder-curients in the sea which bring in the
_
l youngfrywthecoastandthat the fry of the other species do
_
notcomeunder:—the4iiiuenCe of ; these under—eurrents for
Of
But for
it seems more
-
Î;
_
believe. that they actively nd their way there,
j_
’
'
inch long. .…The
ï
-,
Own-particularregion
:
-
:
:î
'.
ï :)
,
Ï
' — '
fsomeWOU1dsaY>thattlïefryaïeadaptedto particular
°°d1tmnsandPenshlftheydonetcomethereandfor£his
,
'
reason wedon0tndthemeXœptunderthese conditions.
THE BIOLOGY OF FISHES
we come to a different set of phenomena. How soon they
choose their own way is uncertain, but we cannot‘regard
.
them any longer as quite helplessly drifting with the currents.
And they' are now able, by swimming, to overcome the
'
difference in specic density between themselves and the
surrounding water—to some extent. Many of the young
larvæ swim actively up to the surface, but when they cease
_
to Swim, they gradually sink. They must keep on the move
_
to remain on the surface.
We may say that on the whole
-
they remain in the body of water surrounding them and are
thus carried along by the currents, but their own activity
in cho'osing the body=of water has to be taken into account.
'
_
Fore‘*æmple, the-fry of the springHerring make their way
_
;froriithe'bottomhp-to;the-Surface and take about three weeks
their ascent ; the y,o_fthe autumn Herring, on the other
.
coihe;upto— the Surface. They remain near
the;Ïwi_nter.… In ,neither case “can
;we; explain the phenomena as«Wholly; due to the
being
'
to particular
-
This is also seen clearly in thecas'e of the Plaice. Wïlienï :
—,
'
_
sinkdown to the bottom, they ought to remain there,
whatever maybe the depth. Yet they only occur near the
_
shore, right on the beach. Redeke, it is true, found some
one—year old Plaice some distance from the coast off Holland ;
.,
but the water there is very shallow and the specimens may
j
out from the shore.
It may be, of course,
thatthereareunder-curients in the sea which bring in the
_
l youngfrywthecoastandthat the fry of the other species do
_
notcomeunder:—the4iiiuenCe of ; these under—eurrents for
Of
But for
it seems more
-
Î;
_
believe. that they actively nd their way there,
j_
’
'
inch long. .…The
ï
-,
Own-particularregion
:
-
:
:î
'.
ï :)
,
Ï
' — '
fsomeWOU1dsaY>thattlïefryaïeadaptedto particular
°°d1tmnsandPenshlftheydonetcomethereandfor£his
,
'
reason wedon0tndthemeXœptunderthese conditions.