(carmine, or Aqua-dag) the pumping rate. in the sea water was found to depress 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. Modiolus has 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 suspended 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 Ulva are reported in the section on algae.