mechanical-that they do not approach the conditions which we are accustomed to re- gard as in a higher sense vital. Yet, even with respect to these, as was brought before you on a former occasion, science does not shrink from the task of ultimately unveiling their mystery. "To suppose," says Darwin,* that the eye, with all its inimitable con- trivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, scems, I freely confess, absurd in the highest possible de- gree. Yet reason tells me, that if numerous gradations, from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shown to exist; if, further, the eye does vary ever so slightly, and the variation be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing 23
- Darwin on the Origin of Species, p. 186.
