Page:Proceedings of the Royal Society of London Vol 60.djvu/252

Rh where n — number of individuals, and a^ and <rB are the standard deviations of organs A and B respectively. This formula has recently been shown by Professor Pearson to be superior to the one formerly used (‘ Phil. Trans.,’ vol. 187).

The correlation surfaces are published as being of permanent value, and it is believed that such material as this will be of use in the future in elaborating or modifying the current theory of correlation.

Pigs. 5 and 6 represent two r lines. The crosses were obtained by

Fig. 5.—R. and L. Anterolateral, r = 0*86.

Variation in Portunus depurator. 231 Dotted line = the r line inclined to axis x at tan""1 0*86. The continuous line joining the crosses is the line found on taking It. antero-lat.. as subject. The circles indicate the points obtained when the L. antero-lat. is the subject. The probable errors of the dimensions are represented by the intervals 1,2, 3, &c., on both horizontal and vertical scales.