The Biology of Balanus balanoides. V. Distribution in the Plymouth Area

1. The barnacles at five localities in the Plymouth area were examined as a check on the general application of observations made previously i n the Isle of Man. 2. The numbers and weights per square metre, and the mean individual weights, are given for a series of tidal levels for each locality. 3. The two “clean-water” localities agree substantially with the Isle of Man, except for the presence here of Chthamalus stellatus. 4. At the three localities where the water is rich in suspended matter first Chthamalus and then Balanus decreases progressively in numbers, but the latter increases very greatly in size, especially at low water. 5. The increased growth rate at low water, where food is abundant, is compared with the similar effect observed in wave-exposed conditions in the Isle of Man.