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DRIFTING LIFE
127
hundred fathoms it is already so dim that few plants
live in & healthy condition.
More will be found on the
subject of the light beneath-the sea surface in Chapter
Although there is a depth limit at which the normal life of
the plant becomes impossible, —-yet at times collections may
_
show their presence at still greater depths, the likelihood
is however that these plants will be in a dying condition
and will have sunk to those depths under their own weight.
N ow
as we know, are not so dependent on light
directly ; in fact there are many animals on land that seem
to
prefer darkness and are nocturnal in their habits, ‘
shunning the light of day.
'
‘
.
.
The same1applies to the sea animals, there‘are many that
live in the dark deep layers ; in fact, recent research has
_
shown that there is no depth at Which some
organisms_ do not exist.
,
'
..
:
All the
not, however, found evenly distributed
in the water layers from top to bottom. Each animal
seems to show a denite…preference for some particular
'
depth region ; foriristance, there are some that live always
in the upper fty _ fathoms or so,
penetratin‘g _to
—
deeper levels ; others again will, never be caught between
one
hundred fathoms
the surface, but always live
deeper.
Onaccount of these differences in depth distrib1i—
tion, exhibited by- the. various animals of the plankton, We
nd that catches made fromdifferent levels are each quite
characteristic
and
distinct
one
from another in
composition, in the same way thatcollections from different
geographical regions are eachcharacterized by the presence
of those organisms that are prevalent in the locality in
which the catch was made.
_
'
,
It is a general fact that in the daytime the
that.
live in the layers quite near the surface are very few, this is
_
especially the case in the summer months. For_instance,
DRIFTING LIFE
127
hundred fathoms it is already so dim that few plants
live in & healthy condition.
More will be found on the
subject of the light beneath-the sea surface in Chapter
Although there is a depth limit at which the normal life of
the plant becomes impossible, —-yet at times collections may
_
show their presence at still greater depths, the likelihood
is however that these plants will be in a dying condition
and will have sunk to those depths under their own weight.
N ow
as we know, are not so dependent on light
directly ; in fact there are many animals on land that seem
to
prefer darkness and are nocturnal in their habits, ‘
shunning the light of day.
'
‘
.
.
The same1applies to the sea animals, there‘are many that
live in the dark deep layers ; in fact, recent research has
_
shown that there is no depth at Which some
organisms_ do not exist.
,
'
..
:
All the
not, however, found evenly distributed
in the water layers from top to bottom. Each animal
seems to show a denite…preference for some particular
'
depth region ; foriristance, there are some that live always
in the upper fty _ fathoms or so,
penetratin‘g _to
—
deeper levels ; others again will, never be caught between
one
hundred fathoms
the surface, but always live
deeper.
Onaccount of these differences in depth distrib1i—
tion, exhibited by- the. various animals of the plankton, We
nd that catches made fromdifferent levels are each quite
characteristic
and
distinct
one
from another in
composition, in the same way thatcollections from different
geographical regions are eachcharacterized by the presence
of those organisms that are prevalent in the locality in
which the catch was made.
_
'
,
It is a general fact that in the daytime the
that.
live in the layers quite near the surface are very few, this is
_
especially the case in the summer months. For_instance,