Dust and sweep as I might, my study continued redolent of ammonia. And then what a slave the birds made of me! The room was shut up at night. The father slept out; so did the mother, after the little ones were beginning to grow up. Then, at early dawn, both were at the windows, in a mighty state of distress outside the glass barrier. With eyes still heavy with sleep, I had to get up hurriedly and let the poor things in. No, I shall not allow myself to be persuaded again; never more shall I permit the Swallow to settle in a room that has to be closed at night and still less in the room where I am describing the misadventures that befel me owing to my too-accommodating kindness. As you see, the Swallow with the nest shaped like a half-cup well deserves his epithet of domestic, inasmuch as he makes his home inside our houses. In this respect, he is among birds what the Pelopæus is among insects. Here we have once again the question of the Sparrow and the Wall-swallow: where did he live before houses existed? Personally, I have never seen him build his nest elsewhere than in the shelter of our habitations; and the authors whom I consult do not appear to be any wiser on this subject. None of them says a word of the manor occupied by the bird apart from the refuges provided by human industry. Can it be that his long frequentation of our society and the consequent sense of comfort have made him forget the primitive customs of his race? I find it difficult to believe: animals are not, to that extent, unmindful of their ancient habits, when it is necessary to remember them. Somewhere, in our day, the Swallow still works independently of us and of our buildings, even as he did in the beginning. Though observation can tell us nothing concerning the site selected, analogy makes up for this silence with a wealth of probabilities. After all, what do our houses represent to the Domestic Swallow? Refuges against the weather, especially against the rain, which does so much harm to the mud shell. Natural grottoes, caves, the irregularities of crumbling rocks: these are all refuges, less healthy, perhaps, but still well worth having. It was here, beyond a doubt, that the Swallow constructed his nest when he had no human dwellings to build in. Man contemporary with the Mammoth and the Reindeer came and shared his lodging under the rock. Intimacy sprang up between the two. Then, step by step, the cave was succeeded by the hut, the hut by the cabin, the cabin by the house; and the bird, abandoning the less good for the better, followed man into his improved abode.