The nest of an ordinary couple contains from twenty five to thirty eggs, but it frequently happens that several couples combine to lay in common. In that case, they form a large enclosure, and the oldest couple are placed in the centre, with the others around them in regular order—so that, if they are four in number, they will occupy the four angles of a square. When the eggs are all laid they are pushed towards the centre, but not mingled together; and when the oldest male comes to sit the others take their places around, where their eggs were laid—and the same with the females. These companies are composed of the young of the same family—in fact, of the young of the oldest couple. They do not all lay the same number of eggs. The one-year olds, for instance, do not lay more than four or five, and those of a small size. At times as many as a hundred eggs are found in the same nest. These family gatherings are most common where the herbage is most abundant. The Arabs have observed a very singular circumstance. The eggs of each couple in these monster nests are carefully piled up together, with one egg conspicuously at the top. It is the one first laid, and it serves for a special purpose. As soon as the male perceives that the moment has arrived for hatching, he breaks with his beak the egg he judges to be the most forward, and at the same time very carefully makes a small hole in the one which surmounts the others. The latter furnishes their first meal to all the young ones as they are hatched, and, though open, will remain sweet for a considerable time. This quality is peculiarly useful; for the male does not break all the eggs on the same day, but only three or four at a time, when he hears the young ones moving inside. The egg which supplies them with nourishment is always liquid, whether through the prevision of nature, or that the old birds have instinctively avoided sitting on it. The fledglings, after having partaken of their first meal, and being speedily dried in the sun, begin at once to run about, and at the end of a few days follow the parent birds to the pasture: in the nest, they always nestle under their wings. The nest is generally of a circular form, and is formed in a sandy soil. The ostrich constructs it with its feet, by simply throwing out the sand from the centre to the circumference. The dust raised by this operation may be seen at some distance. The period of incubation lasts ninety nights. The hunters eat the eggs if they are fresh, and not near ready to be hatched. The shells they either throw away, or take with them, to give as presents to friends, or to deposit them in the _koubba_.[85] However, for some time past, the Arabs have become aware that eggs are an article of traffic on the seaboard, and they now reserve them for that object.