The significance of differences is reported for a given age, based on ( ratios (Table I); and also for the seriatim data, based on the binomial test of significance (sections 2 and 5).* The average ages are approximate, the groups at each age being based on a grade selection.t By Sheldon's classification, 1 ' the average body-build formula was 2.8 -4.4 -3.5 for the early-maturing; 2.4 -3.9 -4.0, for the late-maturing.