. Carnegie Institution of Washington publication. A PHYSIOLOGICAL CHARACTER. 69 600 450 300 the more reactive, the means being 269 and 482 seconds and the difference —213 ± seconds. There is, moreover, an interesting difference noted between every plus brood and every minus brood tested during this period. Without exception the plus broods were considerably more reactive than the minus broods tested at the nearest dates. Such a consistent difference in reactiveness involving every individual brood1 is not generally found in the data obtained from these selection experiments, except in po
. Carnegie Institution of Washington publication. A PHYSIOLOGICAL CHARACTER. 69 600 450 300 the more reactive, the means being 269 and 482 seconds and the difference —213 ± seconds. There is, moreover, an interesting difference noted between every plus brood and every minus brood tested during this period. Without exception the plus broods were considerably more reactive than the minus broods tested at the nearest dates. Such a consistent difference in reactiveness involving every individual brood1 is not generally found in the data obtained from these selection experiments, except in portions of the data for Line 757, in which a pronounced effect of selection was obtained. 750 r 12-1 (913 4-5 8-9 12-1 1914 4-5 8-9 12-1 1915 4-5 8-9 12-1 1916 4-5 8. 150 00 4-5 8-9 1912 12-1 4-5 8-9 1913 12-1 4-5 8-9 1914 12-1 4-5 8-9 1915 12-1 4-5 8-9 1316 FIGURE 10. A, B, C. Reaction-time curves for Daphnia longispina—Lines 762,766, and 768, respectively. D. Composite reaction-time curves for all plus and all minus strains of Daphnia pulex with reaction-time curves for Line 751 superimposed. The divergence in reaction-time means for this last two-month period and particularly the complete and unusual consistency of differences in reaction-time, brood by brood, for this last period suggest an effect of selection. The amount of these data is too small to be more than slightly suggestive, but it seems quite possible that a mutation occurred in the plus strain of Line 762, thus producing 1 It will be remembered that temporary enviromental conditions are very potent factors in modifying the reaction-time means of individual broods and that consequently rather wide fluctuations occur in all the data. Hence, only in cases, in which the reactiveness of the two strains differs greatly do we fail to find the reaction-time means for different broods of the two strains of a line overlapping to a wide Please note that these images are extracted from scanned page images that
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