the sexes. However, the extent to which boys and girls differ in their developmental rate needs further elaboration. Females are ahead of males in the speed with which they move toward physiological maturity, in the eruption of deciduous teeth, in the acquisition of locomotor ability, in the appearance of permanent teeth, in the onset of procreative ability, and in the completion of physical growth. Girls at any age and for any physical trait have attained a larger percentage of their maximum development than have boys of the same age. There is a growth potential related to sex which determines to some extent