62
THE SEAS
sea weed, and has roots for absorbing nutriment from the
*
soil.
In some parts of the Kattegat and 'in the lagoon-like
_
Limijord in Denmark, it covers vast areas.
The associated
fauna_is not very rich ; a little snail called Rissoa is very
plentiful and this is also the haunt of the beautiful green
Haliclystis best dened as
little, squarish jellysh, which
cra—wls about on the eelgrass.
This is the home of ‘sh
such as sticklebacks and pipe—shes,the latter, which have
long, slender, brown or green bodies, being very difcult to
see against the dead and living blades of
They
'
swim in an upright position by the vibration of the delicate
dorsal n, coming to rest in the same position and swaying
'
with the motion of the water.
Closely related to them is
the quaint sea horse.
A number of snails lay their egg
f
capsules on eelgrass, on which, however, there are few
encrusting animals.
_
A large and characteristic'fauna is found on hard bottoms
in the Littoral
There are many attached animals,
notably sponges, sea mats, hydroids, sea squirts and corals,
.
the latter including
“
Dead-men’s-ngers
”
(Alcyonium
digitatum), consisting of dead—white, nger-like growths
covered with tiny polyps (Plate 23), and the little solitary
'
coral, Caryophyllia, which is almost our only example of
true
“
stony
”
Species.
Serpulid worms, which live in
limy tubes and have little plugs ‘for closing the opening
‘
when the. plumose tentacles are withdrawn on the approach
_
of an enemy, are common and also a variety of molluscs
__
like the saddle-oyster, whelk, chiton and, of speçial interest,
.
the delicate bivalve, Lima Mans;
This has a fringe of long
orange tentacles Which cannot be withdrawn within the
shell, but oat in the water and make it
most beautiful
of bivalves.
It has the interesting and very unusual habit
of living in a nest Which it constructs out of pieces of stone
and shell bound together with ne threads. : Sea urchins are