on effect of external influences, [391], [423].
Daucus, structure of root altered by cultivation, [414].
Death, origin of, [20], [21], [143];
relation to reproduction, [21], [120], [132], [154];
necessity of, [23], [24], [134], [159];
utility of, [24], [112], [135], [153];
an adaptation produced by natural selection, [24], [28], [60];
not universal, [25], [27], [111], [119];
by sudden shock, [63];
meaning of, [113];