1 5 5 5.0 5 5 5.0 5.00 2 5 4 4.5 2 2 2.0 3.25 3 4 5 4.5 2 5 3.5 4.00 4 3 4 3.5 1 1 1.0 2.25 5 5 2 3.5 0 1 0.5 2.00 6 3 2 2.5 1 0 0.5 1.50 7 2 1 1.5 1 2 1.5 1.50 8 5 1 3.0 0 0 0 1.50 9 1 3 2.0 0 0 0 1.00 10 1 2 1.5 1 0 0.5 1.00 11 1 1 1.0 0 0 0.50 12 1 1 1.0 0 0 0.50 13 0 0 0 0 0 0 14 0 0 0 0 15 0 0 0 0 [Illustration: FIGURE 33.--Plasticity curves. In the left margin are given the indices of modifiability (the number of tests necessary for the establishment of a perfect habit). Below the base line the age of the individuals is given in months. Curve for males, --•--•--•--; curve for females, - - - -; curve for both males and females,----. When these three plasticity curves are completed, they will represent the indices of modifiability as determined for ten individuals at the age of 1 month, and similarly for the same number of individuals at each of the ages, 4, 7, 10, 13, 16, and 19 months.] The detailed results for the one-month old individuals appear in Table 43; those for the four-month individuals in Table 52. The general averages for the former are to be found in the third column of Table 46, under the heading "10 tests per day"; those for the latter in the last column of Table 52. Mere inspection of these tables reveals the curious sex difference which goes far towards justifying the presentation of this uncompleted work. The index of modifiability for the ten one-month individuals is 88 (that is, 88 tests were necessary for the establishment of a habit); for the four-month individuals it is 102.5. The heavy solid line of Figure 33 joins the points on the ordinates at which these values are located. Apparently, then, the dancer acquires the white-black discrimination habit less readily at the age of four months than at the age of one month.