Abstract
The hooks on 827 statoblasts of a Lake Michigan Pectinatella were counted. The number ranged from 11 to 21; the mode was 13; average, 13.782 ± .031; and index of variability, 1.318±.022. The skewness was + 0.077; that is, the variation tends in the direction of the larger numbers, and this is correlated with the fact that species or races of Pectinatella with much larger numbers of hooks occur. There is a slight hereditary tendency in the statoblasts from one colony, about 0.1 when 1 is the maximum inheritance. There is an inverse correlation (of -.092±.006) between the number of hooks and the perimeter, and a larger one between number and size of hooks. The number of hooks is thus not determined by room, nor does it seem to be predetermined from an early stage of development of the statoblast. The hooks show abnormalities, some of which resemble the normal condition of hooks in Cristatella.
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