THE SEA'SHÔRE
47
occasionally in order to_ moistèn them.
There are also
species of tropical sh," notably.the
“
walking goby,” which
are able to live out of water and even to climb trees; they
have a lung—like extension of the gill chamber, while it is
also reported- that they breathe through their tails, for they
_
sit on the land with only their tails in Water !
.
If held under
water
for any length of time they are drowried.
‘
LOCOMOT_ION AND MIGRATIONS
.
AS we have
many shore animals are attached to
-
rocks or weed or else live inpermanent tubes*or burrows.
_
The advantage. of this mode of life is clear when we consider
the perpetual heating
the waves on the shore as the tide
‘
comes in and goes out.
Of equal advantage is theburrowing
habit of many animals, bivalve molluscs and burrowing
sea
urchins, f0r example,
_
which are also able to move
about beneath the surface.
Movement in. shore animals
'
takes
many
different forms.
"
The
larger 'crustaceans
'
clamber Over rocks and through gullies by means of their
strong, hinged walking legs. The starsh move steadily. over
the surface by the concerted action of the many tiny
“
tubefeet ” each terminated by‘- a Small sucker, double rows of
'
these feet lining the grooves Which run
down the centre of
'
the underside of the arms. "They are connected with a
Complicated system of -canals containing water which can
-
be forced out of or into the tube—feet at will, enabling them
in turn to x and relax their hold.
A similar mode of
movement is found in the Sea urchins, which
also emploÿ
their teeth for this purpose !
A _mussel may move up the
.
side of a rOck by fasténig a byssus thread as
far as possible
—above it andthen pulling itself up by hauling on toit.
.
Some shore sh,such as the ble'nnies, can craw1 over rocks
_
by means of their ns. ' 'The shore insects and the crustacean
sand—hoppers' move by jumping, suddenly straightening
'
47
occasionally in order to_ moistèn them.
There are also
species of tropical sh," notably.the
“
walking goby,” which
are able to live out of water and even to climb trees; they
have a lung—like extension of the gill chamber, while it is
also reported- that they breathe through their tails, for they
_
sit on the land with only their tails in Water !
.
If held under
water
for any length of time they are drowried.
‘
LOCOMOT_ION AND MIGRATIONS
.
AS we have
many shore animals are attached to
-
rocks or weed or else live inpermanent tubes*or burrows.
_
The advantage. of this mode of life is clear when we consider
the perpetual heating
the waves on the shore as the tide
‘
comes in and goes out.
Of equal advantage is theburrowing
habit of many animals, bivalve molluscs and burrowing
sea
urchins, f0r example,
_
which are also able to move
about beneath the surface.
Movement in. shore animals
'
takes
many
different forms.
"
The
larger 'crustaceans
'
clamber Over rocks and through gullies by means of their
strong, hinged walking legs. The starsh move steadily. over
the surface by the concerted action of the many tiny
“
tubefeet ” each terminated by‘- a Small sucker, double rows of
'
these feet lining the grooves Which run
down the centre of
'
the underside of the arms. "They are connected with a
Complicated system of -canals containing water which can
-
be forced out of or into the tube—feet at will, enabling them
in turn to x and relax their hold.
A similar mode of
movement is found in the Sea urchins, which
also emploÿ
their teeth for this purpose !
A _mussel may move up the
.
side of a rOck by fasténig a byssus thread as
far as possible
—above it andthen pulling itself up by hauling on toit.
.
Some shore sh,such as the ble'nnies, can craw1 over rocks
_
by means of their ns. ' 'The shore insects and the crustacean
sand—hoppers' move by jumping, suddenly straightening
'