FEEDING
.
'—
piercing and sucking organs by means of which they feed
—
on the—blood and soft tissues of the sh.
"
,
Ï
.
There“ are also» marine leeches Which suck the blood of
sh. ' The most exàlted of marine parasites is the hagsh,
one of the Cyclostomes and a lowly ally of the‘true sh,
'
which xes itself by a single tooth into the eSh
"
of its
‘
victim and then rasps away the tissues by means of its
'
scaly tongue, sucking in the food as it goes.
'
'
'
The most degenerate types of parasites have completely
lost their feeding organs,‘ they lie in the body cavity or
‘
gut of their host bathed in nutrient uid Which theyabsorb
'
‘
directly through the surface of their bodies.
There are
'
innumerable examples of which only-bne—perhaps the most
striking‘—example can be mentioned here.
It is quite
Common to nd on the under side of ”the bodies ofvarious‘
kinds of crabs, 'a small round brownish mass—rather like
a tumour but in reality a parasite called Sacculina (Plate
80).
It is practically without structure, just a…bag contain—
ing reproductive products with a branching mass
'ofroots
which penetrate thebody of the” crab in all directions and
absorb
nourishment
from
it.
Strangely enough this
_
parasite is a lowly relative of the animal; in which itlives.
'
It is a crustacean mostcloselÿ-allied to the barnacles,‘ a
'
fact WhiCh has been established by study of itslife-history ’
'
(Plate 80).- The eggs, Which are di‘scharged freely into the
sea from the parent parasite, batch out into. minute pear—
shaped creatur€s,
three'pairs of legs, a single
_
_
eye, and “bearing &" littleshell exactly like the similar stage
of any other —crustac€an except that they have no stomach
or intestine.
'These minute. “
Naupliùs ”larvæ (Plate 8o)
swim about in the sea for some weeks when they moult
,
tmd-‘beCome “
Cypris
”
larvæ
have aîhihged— shell
'
"almost enclosing the body, a painof feelers; and some six
pairs of
legs.
"
FOr a little
longèrpthey
'
.
'—
piercing and sucking organs by means of which they feed
—
on the—blood and soft tissues of the sh.
"
,
Ï
.
There“ are also» marine leeches Which suck the blood of
sh. ' The most exàlted of marine parasites is the hagsh,
one of the Cyclostomes and a lowly ally of the‘true sh,
'
which xes itself by a single tooth into the eSh
"
of its
‘
victim and then rasps away the tissues by means of its
'
scaly tongue, sucking in the food as it goes.
'
'
'
The most degenerate types of parasites have completely
lost their feeding organs,‘ they lie in the body cavity or
‘
gut of their host bathed in nutrient uid Which theyabsorb
'
‘
directly through the surface of their bodies.
There are
'
innumerable examples of which only-bne—perhaps the most
striking‘—example can be mentioned here.
It is quite
Common to nd on the under side of ”the bodies ofvarious‘
kinds of crabs, 'a small round brownish mass—rather like
a tumour but in reality a parasite called Sacculina (Plate
80).
It is practically without structure, just a…bag contain—
ing reproductive products with a branching mass
'ofroots
which penetrate thebody of the” crab in all directions and
absorb
nourishment
from
it.
Strangely enough this
_
parasite is a lowly relative of the animal; in which itlives.
'
It is a crustacean mostcloselÿ-allied to the barnacles,‘ a
'
fact WhiCh has been established by study of itslife-history ’
'
(Plate 80).- The eggs, Which are di‘scharged freely into the
sea from the parent parasite, batch out into. minute pear—
shaped creatur€s,
three'pairs of legs, a single
_
_
eye, and “bearing &" littleshell exactly like the similar stage
of any other —crustac€an except that they have no stomach
or intestine.
'These minute. “
Naupliùs ”larvæ (Plate 8o)
swim about in the sea for some weeks when they moult
,
tmd-‘beCome “
Cypris
”
larvæ
have aîhihged— shell
'
"almost enclosing the body, a painof feelers; and some six
pairs of
legs.
"
FOr a little
longèrpthey
'