A Comparison of the Biology of Echinus esculentus in Different Habitats. Part II

Abstract

1. Echinus esculentus was studied from four localities in the Isle of Man and from one in the Clyde.2. The inshore races are thicker shelled and natter, and on all grounds the urchins become taller with increasing age.3. Size distribution measurements on the Chickens material showed a rapid growing period in the spring, followed by cessation of growth for the rest of the year. There is a correlation between amount of growth in a given year, and the sea temperature. On the Breakwater the males and females grow at slightly different times of year.4. Concentric pigmented rings are demonstrated in the test, and are shown to be annual. They are used for estimating the growth rates on the different grounds, which are compared.5. The duration of life is four to eight years, and perhaps more in the very large southern urchins.