The growth of littoral and sublittoral barnacles has been studied in some detail using linear, surface or volumetric measurements (see Barnes & Barnes, 1959). The growth curve in terms of linear dimension generally included an extended straight section which implies, assuming a constant shape, that the volume is increasing with time in proportion to the area (Crisp, 1960). Hence a plot of basal diameter against time is the simplest characteristic of the growth during most of the life of an isolated specimen. In most studies the shells are measured at daily, weekly or monthly intervals and the effect of different factors on growth evaluated. Thus, it has been claimed experimentally that many factors influence directly the growth of barnacles. These factors and their effects are outlined in Table 1.