280
THE BIOLOGY OF FISHES '
_
the Dipnoi or doublebreathingifan‘imals, and '
as— they are highly vascular, With "
numbers of small pockets or‘saccu'li, they’ approach very
closely to the lungs of Higher =Vertebrates.
In the dry
î
,
season of the year the South American Lepidosiren and the
_i
African Protopte'rus bury themselves in the mud and can'
remain there for nearly half a year. Even in the water they
,
come. up to the surface fromtime to time, like» porpoises;
to empty their lungs and take in a fresh supply of air. The
'
QueenslandNeoceratodus does the same thing, but does
.—
not
seem, to
bufy itself at any time.: The adaptation,
therefore, has arisen in the water,
like the
other
shes, or the accéssory breathing organs of the Anabantoids.
,
"
The two speCies of Dipnoi
like the Higher
Vertebrates, have simply made
more special use of an
organ Or
that had alreadyiheen acquired.
'
"be
a sac of some kind of
other has been found by Stàrks
in the
_
abdominal…cavity of an Ophiocephalid; As in ”the rest of
this family the air-bladder is exceptionally large,, but this?
nextra sac, though closely apposed to it, has no
,
'
tion Withthe air—jb'ladder'and'opens tothe exteri0r through:
:
genital pore.
'
condition of things
1136;
be present in other shes also,an‘d it 15
__.Î
a regulating mechanism—- for
Of air.
the
'
,
frequently'b‘esnafoundWithaconserableqUanüty0fwater
'
:
of breath1ng—valves,thefoodandsohdobpcts entering by
’
_'themouthhaveledtootheradaptauons 'The gill—laments { -ÏÈî
—
”
?"ÿare
margins ' ofithe
yarches
anterior marginsfï wenda
_
Ÿ
_' ‘flparallel series of
-‘so—called '
'
fake the ïgills, as a
fact,
'
'
:
__
Ç
to.—the
We
'
—