~12-
(carmine, or Aqua-dag) in the sea water was found to depress
the pumping rate.
Suspensions of the order of 0.001 per cent
cause a reduction of about 15 per cent at 12°C.
suspensions of carmine
With heavy
(0.1 per cent) the pumping becomes erratic
with periods of one minute or less of more rapid rates than
normal and periods of ten to thirty seconds of cessation of
pumping.
Pumping of 300 to 400 cc is followed by sudden closure
with the forceful ejection of pseudofeces.
Modiolushas been
found to be extremely sensitive to vibrations; even the activation of sump pumps in the building could be detected by
momentary cessation or depression of the pumping rate, although
there was no accompanying shell movement.
This was not fully
appreciated at the time most of the runs on the effect of sus-
pended material were made.
repeated.
Mytilus.
These will consequently have to be
No tidal rhythm was noted as has been reported for
It is hoped these experiments can be resumed in July
1954.
Several local marine gastropods and the shore crab,
Hemigrapsus nudus, have been brought into the laboratory and
tested for suitability for cycling experiments with Chlorella
and Ulva.
Thus far only Hemigrapsus has been found to be suf-
ficiently predictable in its appetite and easily manageable.
Results of preliminary feeding experiments with Ulvaare
reported in the section on algae.