The rate of development of the embryos of Balanus balanoides (L.) from a number of european and American populations and the designation of local races

A summary is given of the distribution of Balanus balanoides (L.) and of earlier work on differences — racial and otherwise. The variation in the date at which different populations are fertilized is considered. Data are given on the time required for the development of the embryos of this species in vitro at 10 °C, with eggs from a number of populations from the eastern and western Atlantic and examined soon after collection, and also after transplantation and maintenance under ambient laboratory conditions over the next breeding season. Both aspects of reproduction are under genetic control. There is no correlation between the date of fertilization and the time required for development.Oocyte and egg size appear to be largely controlled by temperature.On both sides of the Atlantic there is a general tendency for the time of development to decrease with decreasing latitude. The population at Millport, Scotland appears unusual. The southernmost populations on European shores resemble those at the extreme south in North America.A study of the effect of temperature has shown that at lower temperatures the time of development of the embryos in vitro from all populations tends to be the same; the difference lies in the Q₁₀ values.The results are discussed relative to palaeontological data and the existence of clines in other features.