The annual cycle of some physiological conditions in the ormer, Haliotis tuberculata L. was studied by the C:N ratios of foot tissue which were convertible to the glycogen contents, and the coefficients of fatness calculated from two formulae. The former method showed the seasonal change inrelation to the reproductive cycle indicating the foot tissue as a nutritive storage reservoir for spawning, and the latter gave no clear seasonal fluctuation, except a drop of the value shortly afterspawning.

Comparison of ormer populations representing local sites in Guernsey was made by the two methods during the periods of gonad maturation, spawning and pre-spawning (May-October), and the shell forms were analysed by measuring three dimensions of shells, namely, shell length, width and height. The results revealed some changes in physiological conditions between different localities and seasons even within Guernsey. The shell forms also appeared to differ at each site probably as a reflexion of physical and biological conditions surrounding them. The relation of the results obtained by all the methods was discussed to give a more generalized account on physiological conditions of the ormer for its reproduction.