premise: With due consideration for the limits of precision in assessing , expected rate of change in <mask> of girls age 2 years , and the known variations in rate of <mask> of these children as described in our preceding paper in the Supplement , each arrow with a `` shaft length '' of four months or less was selected as indicating `` same schedule '' at Onset and Completion , for this particular epiphysis .
hypothesis: the proper context for <mask> here should be the developmental process of bone formation