The character of the after-effect will presently be shown to be modified by the duration of previous stimulation, the different phases of which will for convenience, be distinguished as pre-maximum, maximum and post-maximum. Since stimulus simultaneously induces positive "A" and the negative "D" changes (p. 143), their intensities will undergo relative variation during the continuance and cessation of stimulus. The after-effect will therefore exhibit unequal persistence of the expansive "A" and contractile "D" reaction at different phases of stimulation. ELECTRIC AFTER-EFFECT. Confining our attention to the electric response, it is found that under continued action of light the excitatory galvanometric negativity increases to a maximum, after which there is a decline, and neutralisation. Figure 205 gives the galvanographic record of the electric response of the leaf stalk of _Bryophyllum_ under light; the up-curve represents increasing negativity which, after attaining a maximum, undergoes neutralisation as seen in the down-curve. I shall, with the help of the diagram given in the next figure, describe and explain the various after-effects I observed on sudden stoppage of light: before the attainment of maximum, at the maximum, and after the maximum. [Illustration: FIG. 205.--Electric response of the leaf-stalk of _Bryophyllum_ under continuous photic stimulation. Increasing negativity represented by up-curve; neutralisation by down-curve.] [Illustration: FIG. 206.--Diagrammatic representation of electric after-effect of stimulation. Pre-maximal stimulation produced by stoppage of light at _a_, gives rise to continuation of previous response followed by recovery. Stoppage of light at maximum _b_ gives rise to recovery to equilibrium position. Stoppage of light at post-maximum _c_, gives rise to over-shooting below zero line.] _After-effect of pre-maximum stimulation: Experiment 214._--Light is applied at arrow and stopped in different experiments at _a_, _b_, and _c_ (Fig. 106). Continuous stimulation induces increasing galvanometric negativity; when stimulus is stopped at _a_ before the maximum, the after-effect is a persistence of excitatory galvanometric negativity, which carries the response record higher up; after a certain interval recovery takes place and the record returns to the zero line of normal equilibrium. The after-effect of pre-maximum stimulation is thus a short-lived continuance of response followed by recovery. _After-effect at maximum: Experiment 215._--In this the photic stimulus was continued till the attainment of maximum, when light was suddenly removed at _b_. The after-effect was no longer a persistence of responsive movement, but disappearance of negativity and recovery to zero line of equilibrium.