these agents has an effect on hair development if applied during the active phase. When applied during the inactive phase, the phosphate solution produces epilation and initiates hair regeneration, while the benzene and ether, in addition to these effects, produce inflammation and thickening of the skin and scab formation. In all cases the rate of development and the ultimate product are normal. It appears that the initiation of development is the primary effect of treatment and that epilation is a separate effect. It is suggested that these agents may stimulate the hair germ indirectly through the external sheath. The increase in blood supply, at least for benzene and ether, may also be a factor. It is concluded that the truly critical stage in the developmental cycle with regard to the effects of certain external influences is not the stage of active hair formation but rather the developmentally inactive phase. The resting period may be shortened, but the rate of growth, once initiated, is not changed.