Observations on Periodicity in Marine Invertebrates

Arising from field observations of marine fouling in Sydney Harbour, a study was made of planktonic larvae and fouling settlement to see whether the peculiar results observed in the field could be due to a tidal periodicity. While not conclusive, there is evidence of periodicity which may be related to tides. Periodicity was observed in the distribution of lamellibranch and polychaete larvae in the plankton and in the settlement of Balanus amphitrite Darwin and Hydroides norvegica Gunnerus.