It is impossible, we must admit, to fix dates, except in a few cases, relatively recent; but there is a smack of modernity in some striking devices which we can observe in operation to-day. Thus no one will dispute the statement that spiders are thoroughly terrestrial animals breathing dry air, but we have the fact of the water-spider conquering the under-water world. There are a few spiders about the seashore, and a few that can survive douching with freshwater, but the particular case of the true water-spider, _Argyroneta natans_, stands by itself because the creature, as regards the female at least, has _conquered_ the sub-aquatic environment. A flattish web is woven, somehow, underneath the water, and pegged down by threads of silk. Along a special vertical line the mother spider ascends to the surface and descends again, having entangled air in the hairs of her body. She brushes off this air underneath her web, which is thereby buoyed up into a sort of dome. She does this over and over again, never getting wet all the time, until the domed web has become like a diving-bell, full of dry air. In this eloquent anticipation of man's rational device, this creature--far from being endowed with reason--lays her eggs and looks after her young. The general significance of the facts is that when competition is keen, a new area of exploitation is a promised land. Thus spiders have spread over all the earth except the polar areas. But here is a spider with some spirit of adventure, which has endeavoured, instead of trekking, to find a new corner near at home. It has tackled a problem surely difficult for a terrestrial animal, the problem of living in great part under water, and it has solved it in a manner at once effective and beautiful. In Conclusion We have given but a few representative illustrations of a great theme. When we consider the changefulness of living creatures, the transformations of cultivated plants and domesticated animals, the gradual alterations in the fauna of a country, the search after new haunts, the forming of new habits, and the discovery of many inventions, are we not convinced that Evolution is going on? And why should it stop? VII THE DAWN OF MIND THE DAWN OF MIND In the story of evolution there is no chapter more interesting than the emergence of mind in the animal kingdom. But it is a difficult chapter to read, partly because "mind" cannot be seen or measured, only _inferred_ from the outward behaviour of the creature, and partly because it is almost impossible to avoid reading ourselves into the much simpler animals. Sec. 1 Two Extremes to be Avoided The one extreme is that of uncritical generosity which credits every animal, like Brer Rabbit--who, by the way, was the hare--with human qualities. The other extreme is that of thinking of the animal as if it were an automatic machine, in the working of which there is no place or use for mind. Both these extremes are to be avoided.