FOOD QUESTION
307
and, it may
said, still maintained by most 'biologists,
—shes are dependent for their food on organised bodies, that
is, on forms that already contain protoplaSm or living
matter.
_Pütter, however, is of the opinion that the tissues,
gills and alimentary- canal, even the skin in young forms,
are
able to absorb organic and inorganic substances dis—
solved in the water.
If living OrganiSms could make
plete use 0f the food-stuë they take‘ into themselves, the
end—products would be simply water and carbonic acid,
but in most cases the assimilation is incOmplete and large
qu-antities of other metabolic products are set“ free in the
water.
The most abundant of these“ are thecarbohÿdrates
(sugare), but
Compounds (free‘ or in
noids) andÏph08ph‘ates Or phosphoric acid alSo occur. It
has. been found also, that the latter are present in the water
of the sea and:that their quantity varies in dieænt places
and even in the same Water at different levels and different
Seasons
of the year (Matthews, 1916; Raben, 1916). 'If
Pütter’s views prove to be correct, this variation may be of
importance to the young shes; =
-
«'
>”
'
'SO'me
bbdies, bacteria and“ '
-
parasites Without digestive traCt, are able to absorb dissolved
_0rganic
into their- bodies,‘ and the question is
how far thisÏ- may ocCur in shés. The pœsibility-iS n0t to
_
be" eX'cliided Without Careful '- investigation. ÂThe Leptd—
cephali of the‘Eel, as notedin Chap. HI (Fig. 'Iz),sPend
three years out in the‘AtlantiC, and—very little food has beenfound in their digestive tract, especially in the third
It,has‘_ been assumed that they live on
the nannoplankton,
microscopic organisms that escape through the meshes of
nets, but we know as little about these
as aout the imp“orÏtanCe of the dissolved organic substances;
Theî“factÈthat the-whole internal structure of the Lepto—
cephalùS is bathed'in a watery uid, which may‘
access from and to the exterior, suggests that 'it
,
general purposes of” respiration, digestion and “‘eXC'retion;
'
Again the young , Of vivipàro‘us‘ shes
'
tocids, and others) spend
body
of the“
307
and, it may
said, still maintained by most 'biologists,
—shes are dependent for their food on organised bodies, that
is, on forms that already contain protoplaSm or living
matter.
_Pütter, however, is of the opinion that the tissues,
gills and alimentary- canal, even the skin in young forms,
are
able to absorb organic and inorganic substances dis—
solved in the water.
If living OrganiSms could make
plete use 0f the food-stuë they take‘ into themselves, the
end—products would be simply water and carbonic acid,
but in most cases the assimilation is incOmplete and large
qu-antities of other metabolic products are set“ free in the
water.
The most abundant of these“ are thecarbohÿdrates
(sugare), but
Compounds (free‘ or in
noids) andÏph08ph‘ates Or phosphoric acid alSo occur. It
has. been found also, that the latter are present in the water
of the sea and:that their quantity varies in dieænt places
and even in the same Water at different levels and different
Seasons
of the year (Matthews, 1916; Raben, 1916). 'If
Pütter’s views prove to be correct, this variation may be of
importance to the young shes; =
-
«'
>”
'
'SO'me
bbdies, bacteria and“ '
-
parasites Without digestive traCt, are able to absorb dissolved
_0rganic
into their- bodies,‘ and the question is
how far thisÏ- may ocCur in shés. The pœsibility-iS n0t to
_
be" eX'cliided Without Careful '- investigation. ÂThe Leptd—
cephali of the‘Eel, as notedin Chap. HI (Fig. 'Iz),sPend
three years out in the‘AtlantiC, and—very little food has beenfound in their digestive tract, especially in the third
It,has‘_ been assumed that they live on
the nannoplankton,
microscopic organisms that escape through the meshes of
nets, but we know as little about these
as aout the imp“orÏtanCe of the dissolved organic substances;
Theî“factÈthat the-whole internal structure of the Lepto—
cephalùS is bathed'in a watery uid, which may‘
access from and to the exterior, suggests that 'it
,
general purposes of” respiration, digestion and “‘eXC'retion;
'
Again the young , Of vivipàro‘us‘ shes
'
tocids, and others) spend
body
of the“