The General Biology of Balanus balanus (L.) Da Costa

as Maine on the east American coast and to the shores of Britain. While there is a good deal known about its distribution (see BROCH, 1924) with the exception of a recent study of its breeding habits in the Irish Sea -(CRIsP, 1954 there is little detailed information on its general biology. It is a common sub-littoral barnacle in the Clyde Sea Area, being found widely dispersed on suitable rough ground. It has been found at all depths down to 60 metres, and although more commonly between 20-30 metres, this may merely reflect the fact that it is at these depths that suitable substrata occur in this area. Observations have been made of its occurrence in the area, but the regular collections, on which this account is largely based, were taken between Little and Great Cumbrae at a depth of about 20 metres. The distribution does not appear to be regular even over quite a restricted area, but the population density at this point is very high (see later). Samples were taken with a small dredge, the stones and shells being usually covered with barnacles, often distorted from the typical shape because of overcrowding. The tidal currents at this point are quite strong, and this and the rough stony and shelly bottom appear to be excellent conditions for this species. On these grounds B. balanus is often, indeed usually, mixed with the other common sub-littoral cirripede in this area, B. crenatus. The other associated species are those commonly found on this type of mixed rough ground and the following list indicates those most commonly taken.