THE SEA BOTTOM
57.
matter having been dissolved away on its passage'downward
‘_
through the water.
In certain areas, notably in the tropical
,
‘
regions of the Pacic and Indian oceans, there are great num—
bers of minute animals known as Radiolarians in_thesurface
waters ; these have skeletons of silica, often ofvery beauti—
ful lattice design, which form the most conspicuous part
'
of the deep—sea ooze in theseregions (Plate 21).- Finally,
at the greatest depth of all (below 2,700 fathoms) even the
.
silica is dissolved and the depositsthen ;consist —exClusively
of what Murray called “ red clay.”
Ibis is a trueclay
which has been formed by the prolonged action of the sea
water on volcanic dust which is allthat has survived the
_
long journey from the surface to the
Like the
siliceous deposits it is present at all depths but is,usually
.
masked by the -deposits ofanimal or plant origin.
In this
-
red clay are found spherules probably of “meteoritic Origin,
and also the completely insoluble teeth of sharks+so1e of
-
which belong to extinct
ear—bones of whales.
'
Although the actual substance of the sea bottomhas —not
the same overw—helming importance as the-”soil on' land, Since
»
even
the sea Weeds do not*root in it, merely attaching
themselves to rocks, andŸ obtain all their nourishment from
the substances in solution in the Water, yet it.has co‘nsider.
able importance.. In'the rst place it is of use to the bottom
animals which may crawl on its surface, burrow into
it. or attach themselves to it. 'The‘naturè of the bottom—
sand, mud, gravel or rock—is of the rst importance to
them.
Most of the animals collected from the bottom do
.
not live on the surface of this but burrow into it. _Each bur—
rower is adapted for -excavating in_—a particular substratùm
'
—sand, shell grax*el, muddy shell gravel, or mud.
This explains Why we invariably collect a particular group of
animals from each of these localities.
I—n some cases an ap—
pareritly triing difference between two species may enable
57.
matter having been dissolved away on its passage'downward
‘_
through the water.
In certain areas, notably in the tropical
,
‘
regions of the Pacic and Indian oceans, there are great num—
bers of minute animals known as Radiolarians in_thesurface
waters ; these have skeletons of silica, often ofvery beauti—
ful lattice design, which form the most conspicuous part
'
of the deep—sea ooze in theseregions (Plate 21).- Finally,
at the greatest depth of all (below 2,700 fathoms) even the
.
silica is dissolved and the depositsthen ;consist —exClusively
of what Murray called “ red clay.”
Ibis is a trueclay
which has been formed by the prolonged action of the sea
water on volcanic dust which is allthat has survived the
_
long journey from the surface to the
Like the
siliceous deposits it is present at all depths but is,usually
.
masked by the -deposits ofanimal or plant origin.
In this
-
red clay are found spherules probably of “meteoritic Origin,
and also the completely insoluble teeth of sharks+so1e of
-
which belong to extinct
ear—bones of whales.
'
Although the actual substance of the sea bottomhas —not
the same overw—helming importance as the-”soil on' land, Since
»
even
the sea Weeds do not*root in it, merely attaching
themselves to rocks, andŸ obtain all their nourishment from
the substances in solution in the Water, yet it.has co‘nsider.
able importance.. In'the rst place it is of use to the bottom
animals which may crawl on its surface, burrow into
it. or attach themselves to it. 'The‘naturè of the bottom—
sand, mud, gravel or rock—is of the rst importance to
them.
Most of the animals collected from the bottom do
.
not live on the surface of this but burrow into it. _Each bur—
rower is adapted for -excavating in_—a particular substratùm
'
—sand, shell grax*el, muddy shell gravel, or mud.
This explains Why we invariably collect a particular group of
animals from each of these localities.
I—n some cases an ap—
pareritly triing difference between two species may enable