animals; and in their lake-dwellings they collected hints from five sources: natural bridges, the platforms built by anthropomorphous apes,[34] the habits of waterfowl, the beavers dam and “lodge,” and the nests of birds. In the round hut, which was made with branches and wattle-and-daub, stick nests were united to the plasterwork of rock-martins. Yes, a good workman in the construction of mud walls does no more than rock-martins have done in all the ages of their nest-building. When these birds make their nests they use wet loam stiffened with bits of straw, and each layer is allowed to harden before another is put on in a thickness of about half an inch for a day’s work.[35] Even more remarkable is the fact that men may have borrowed from several birds the idea which enabled them to pass from round huts into oblong cabins. In Australia, for instance, there are three birds--genera of the same family--that build arched bowers with long sides; and Darwin tells us to regard them as “co-descendants of some ancient species which first acquired the strange instinct of constructing bowers for performing their love-antics.” One species of Australian bower-birds, the fawn-breasted variety, erects a platform of sticks as a foundation for its gabled hall of courtship, that measures nearly four feet in length and eighteen inches in height. This structure is charmingly decorated, and if we could magnify it to the size of Westminster Hall we should be amazed by its beautiful architecture. Unmagnified, it is a model to all primitive men, for it shows far more invention than a wigwam or than a charcoal-burner’s hut. As soon as a student begins to understand what mankind has copied in Nature’s wonderful school for mimics, he cannot fail to take delight in natural bridges and their influence on handicraft. At first he is humbled painfully by the small amount of creative wit that a million years or so have gleaned from the big human brain; but soon the novelty of feeling humble is more attractive to him than the vile habit of flattering human nature.[36] II AMONG THE HERALDS OF MAN It was during the Upper Miocene age that two or three big apes migrated into Europe, probably from Africa, and passed from explorers into colonists. One of them was the Dryopithecus, a creature almost as tall as a man, and closely allied to Hylobates. He illustrated that organic art of caricature in which young Dame Nature excelled, many of her experimental efforts having Gargantuan humour in their shapes and proportions.