The English writer to whom I have referred says that the wren builds the outside of its nest of old hay straws when placing it in the side of a rick, of green moss when it is situated in a mossy bank, and of dead leaves when in a hedge-row or a bramble-bush, in each case thus rendering the nest very difficult of detection because it harmonizes so perfectly with its surroundings, and the writer wonders if this harmony is the result of accident or of design. He is inclined to think that it is unpremeditated, as I myself do. The bird uses the material nearest to hand. Another case, which this same writer gives at second-hand, of a bird recognizing the value of protective coloration, is not credible. A friend of his told him that he had once visited a colony of terns "on an island where the natural breeding accommodation was so limited that many of them had conveyed patches of pebbles on to the grass and laid their eggs thereon." Here is the same difficulty we have encountered before--one more step of reasoning than the bird is capable of. As a deduction from observed facts, a bird, of course, knows nothing about protective coloring; its wisdom in this respect is the wisdom of Nature, and Nature in animal life never acts with this kind of foresight. A bird may exercise some choice about the background of its nest, but it will not make both nest and background. Nature learns by endless experiment. Through a long and expensive process of natural selection she seems to have brought the color of certain animals and the color of their environment pretty close together, the better to hide the animals from their enemies and from their prey, as we are told; but the animals themselves do not know this, though they may act as if they did. Young terns and gulls instinctively squat upon the beach, where their colors so harmonize with the sand and pebbles that the birds are virtually invisible. Young partridges do the same in the woods, where the eye cannot tell the reddish tuft of down from the dry leaves. How many gulls and terns and partridges were sacrificed before Nature learned this trick! I regard the lower animals as incapable of taking the step from the fact to the principle. They have perceptions, but not conceptions. They may recognize a certain fact, but any deduction from that fact to be applied to a different case, or to meet new conditions, is beyond them. Wolves and foxes soon learn to be afraid of poisoned meat: just what gives them the hint it would be hard to say, as the survivors could not know the poison's deadly effect from experience; their fear of it probably comes from seeing their fellows suffer and die after eating it, or maybe through that mysterious means of communication between animals to which I have referred in a previous article. The poison probably changes the odor of the meat, and this strange smell would naturally put them on their guard.