/o ;z /¥ Iff /s zo zzHp 



Fig. 27. Dimensional structure of populations of Mi noli a iridescens (a) 

 and Littorina squalida (b) during the summer in Pos'yeta Bay, Sea of 

 Japan. Ordinate shows number of individuals (N) per n&; abscissa shows 

 shell height, mm. 



ears 



Fig. 28. Linear growth of Minolia iridescens (a) and Littorina squalida 

 (b) in Pos'yeta Bay, Sea of Japan. Ordinate shows shell height (Hp), 

 mm; abscissa shows age, years. 



The essence of determination of growth rate and life duration of 

 individuals in a specific population can be reduced to counting the 

 number of corresponding generations of discrete dimensional -wei ght 

 groups. In species with life cycles over 1 year in length, the first 

 dimensional -wei ght group, depending on the time of sampling and the 

 status of the population, corresponds to individuals born in the same 

 year, or individuals at least 1 year of age, while the second belongs to 

 individuals a year older, etc. With spawning in portions, extended 

 metamorphosis or the formation of spring and winter subgenerations, 

 individuals of a given year of birth form similar dimension and weight 

 groups, corresponding to the spawning peaks, and different from each 

 other in terms of dimensions and weight significantly less than 

 individuals of the previous year of birth. The reliability of 

 differences in dimensions of individuals of successive generations is 

 usully tested by statistical methods. In an analysis of the structure 



306 



