We saw that conduct is distinguished from the totality of actions by excluding purposeless actions; but during evolution this distinction arises by degrees. In the very lowest creatures most of the movements from moment to moment made, have not more recognizable aims than have the struggles of an epileptic. An infusorium swims randomly about, determined in its course not by a perceived object to be pursued or escaped, but, apparently, by varying stimuli in its medium; and its acts, unadjusted in any appreciable way to ends, lead it now into contact with some nutritive substance which it absorbs, and now into the neighborhood of some creature by which it is swallowed and digested. Lacking those developed senses and motor powers which higher animals possess, ninety-nine in the hundred of these minute animals, severally living for but a few hours, disappear either by innutrition or by destruction. The conduct is constituted of actions so little adjusted to ends, that life continues only as long as the accidents of the environment are favorable. But when, among aquatic creatures, we observe one which, though still low in type, is much higher than the infusorium--say a rotifer--we see how, along with larger size, more developed structures, and greater power of combining functions, there goes an advance in conduct. We see how by its whirling cilia it sucks in as food these small animals moving around; how by its prehensile tail it fixes itself to some fit object; how by withdrawing its outer organs and contracting its body, it preserves itself from this or that injury from time to time threatened; and how thus, by better adjusting its own actions, it becomes less dependent on the actions going on around, and so preserves itself for a longer period. A superior sub-kingdom, as the Mollusca, still better exemplifies this contrast. When we compare a low mollusc, such as a floating ascidian, with a high mollusc, such as a cephalopod, we are again shown that greater organic evolution is accompanied by more evolved conduct. At the mercy of every marine creature large enough to swallow it, and drifted about by currents which may chance to keep it at sea, or may chance to leave it fatally stranded, the ascidian displays but little adjustment of acts to ends in comparison with the cephalopod; which, now crawling over the beach, now exploring the rocky crevices, now swimming through the open water, now darting after a fish, now hiding itself from some larger animal in a cloud of ink, and using its suckered arms at one time for anchoring itself and at another for holding fast its prey; selects and combines and proportions its movements from minute to minute, so as to evade dangers which threaten, while utilizing chances of food which offer: so showing us varied activities which, in achieving special ends, achieve the general end of securing continuance of the activities.