_
THE SEA SHORE
.
29
all be plant fee‘ders and live on Weed, they may all be
attached forms and live fastened to rocks, or be burrowers
into mud or sand, or they maybe carnivorous beasts which
prey upon the animals composing one of thesecommunities
.
to
which
they thereby become attached.
The
most
intimate form of association is that of parasite and host (as
_
we call the animal which “ entertains ” the parasite), or the
more equal type of intimate union known as symbiosiS,.
’
some
account of Which is given on page 213. Lastly,
animals, without being actually united with one another,
may always live together, one perhaps upon the other, a
Condition called commensalism, because the two feed iii
common and also frequently assist one another.
Examples
of this are given later in this chapter.
'
.
We can recognize a series of fairly denite zones as we
pass down from high—water mark over the shore at dead
'
,.
water.
On rocky-shows we can distinguish these zones
'
.
by the different levels at which the principal sea weeds
grow. , The
different coloured weeds have' a perfectly
denite arrangement, the green ones generally growing in '
;
pools near high-water mark- or. even above ”it where sea
water only occasionally penetrates and the water is largely
fresh; the brown weeds arexespecially common between
tide—marks, as no one who has ever walked ”on a rocky
shore can fail to have realized, while below them come the
red weeds. These are usually found between tide-marks at
the bottom of the deeper rock pools orwhen the spring
"
tide uncovers an‘exceptionally large area, but are Commonest
"
in shallow water off a rocky shore.
.
'
__
Above high—water
at the.highest spring
.tides, there .is an
of mixed salt and fresh water—
brackish is the term used to describe it——which, if the ground
be marshy, is usually'cha‘racterized by the presence of the
_
’
little salt-wort, a tinyplant' (not a: sea weed) which has)
THE SEA SHORE
.
29
all be plant fee‘ders and live on Weed, they may all be
attached forms and live fastened to rocks, or be burrowers
into mud or sand, or they maybe carnivorous beasts which
prey upon the animals composing one of thesecommunities
.
to
which
they thereby become attached.
The
most
intimate form of association is that of parasite and host (as
_
we call the animal which “ entertains ” the parasite), or the
more equal type of intimate union known as symbiosiS,.
’
some
account of Which is given on page 213. Lastly,
animals, without being actually united with one another,
may always live together, one perhaps upon the other, a
Condition called commensalism, because the two feed iii
common and also frequently assist one another.
Examples
of this are given later in this chapter.
'
.
We can recognize a series of fairly denite zones as we
pass down from high—water mark over the shore at dead
'
,.
water.
On rocky-shows we can distinguish these zones
'
.
by the different levels at which the principal sea weeds
grow. , The
different coloured weeds have' a perfectly
denite arrangement, the green ones generally growing in '
;
pools near high-water mark- or. even above ”it where sea
water only occasionally penetrates and the water is largely
fresh; the brown weeds arexespecially common between
tide—marks, as no one who has ever walked ”on a rocky
shore can fail to have realized, while below them come the
red weeds. These are usually found between tide-marks at
the bottom of the deeper rock pools orwhen the spring
"
tide uncovers an‘exceptionally large area, but are Commonest
"
in shallow water off a rocky shore.
.
'
__
Above high—water
at the.highest spring
.tides, there .is an
of mixed salt and fresh water—
brackish is the term used to describe it——which, if the ground
be marshy, is usually'cha‘racterized by the presence of the
_
’
little salt-wort, a tinyplant' (not a: sea weed) which has)