88
EFFECT OF TRAWLING ON SPONGES AND zoornrrns.
'
'.
_
since the West Sands at St Andrews have been so extensively
covered with marine organisms in débris, as, for instance, in
the spring of 1857, when the misty air was alive with hooded
crows
and gulls that fed on the stranded animals. Sfnaller ‘
numbers have been seen, but not the vast numbers of sea-mice,
_
sea—_urchins, star-shes, shell—shes, zoophytes, crabs, and other
,
forms.
Besides the evidence (and there is much) of the capture
and injury of the invertebrates in the trawl, and the consequent removal of part of the food of the shes at the bottom,
it is necessary to show that by constant trawling the sea—bottom
.
is rendered destitute of nourishmeht for the food—shes.
Nature
has provided in the case of such forms a remarkable power
of
_
-:
.
recuperation, and a vitality that renders complete destruction
_
'
difcult.
Thus, the crushing and division of sponges is not
followed by the death of all the fragments, and each of those
which survives is capable of ourishing as an independent
organiSm (not to allude to the liberation of eva which may
_
happen to be present). The ordinary zoophytes are, as a rule,
_
little affected by being carried on board ship, for, though in
_
the more delicate, such as Tabularia, the soft polypites may
fall off, they are reproduced when returned to the water.
The
'
very general provision of free—swimming buds which bear
-
_
reproductive elements is also a complete safeguard in
_
of this group, as already stated.
Whence do the:
immense multitudes of the zoophyte (Obelia), which coats with
a feathery forest every r'ope and buoy of the salmon stake—nets,
a
come?
Certainly not from the bottom, but from the myriads'
_
;
minute pelagic jelly—shes.
Each half of a bisected anemone
Ï
becomes an independent animal. Again, the ‘sand-dwelling
_
forms, such as Peachia and Edwadsia, the latter
'
_
-
eaten by ounders and dabs, have pelagic young which are
swept in every direction by the currents, or sometimes are
carried
hither
_
and thither attached
to the disks of the ',
swimming
These forms are, indeed,
‘
_
tected, since they live in the sand, and are seldom -or never
'
captured by the trawl, While '
their young are wholly pelagic. :
‘The
masses of dead
men’s
ngers (AZC3/O7tiüt), though
_
EFFECT OF TRAWLING ON SPONGES AND zoornrrns.
'
'.
_
since the West Sands at St Andrews have been so extensively
covered with marine organisms in débris, as, for instance, in
the spring of 1857, when the misty air was alive with hooded
crows
and gulls that fed on the stranded animals. Sfnaller ‘
numbers have been seen, but not the vast numbers of sea-mice,
_
sea—_urchins, star-shes, shell—shes, zoophytes, crabs, and other
,
forms.
Besides the evidence (and there is much) of the capture
and injury of the invertebrates in the trawl, and the consequent removal of part of the food of the shes at the bottom,
it is necessary to show that by constant trawling the sea—bottom
.
is rendered destitute of nourishmeht for the food—shes.
Nature
has provided in the case of such forms a remarkable power
of
_
-:
.
recuperation, and a vitality that renders complete destruction
_
'
difcult.
Thus, the crushing and division of sponges is not
followed by the death of all the fragments, and each of those
which survives is capable of ourishing as an independent
organiSm (not to allude to the liberation of eva which may
_
happen to be present). The ordinary zoophytes are, as a rule,
_
little affected by being carried on board ship, for, though in
_
the more delicate, such as Tabularia, the soft polypites may
fall off, they are reproduced when returned to the water.
The
'
very general provision of free—swimming buds which bear
-
_
reproductive elements is also a complete safeguard in
_
of this group, as already stated.
Whence do the:
immense multitudes of the zoophyte (Obelia), which coats with
a feathery forest every r'ope and buoy of the salmon stake—nets,
a
come?
Certainly not from the bottom, but from the myriads'
_
;
minute pelagic jelly—shes.
Each half of a bisected anemone
Ï
becomes an independent animal. Again, the ‘sand-dwelling
_
forms, such as Peachia and Edwadsia, the latter
'
_
-
eaten by ounders and dabs, have pelagic young which are
swept in every direction by the currents, or sometimes are
carried
hither
_
and thither attached
to the disks of the ',
swimming
These forms are, indeed,
‘
_
tected, since they live in the sand, and are seldom -or never
'
captured by the trawl, While '
their young are wholly pelagic. :
‘The
masses of dead
men’s
ngers (AZC3/O7tiüt), though
_