The nest of an ordinary pair contains from twenty-five to thirty eggs. But it often happens that several couples unite to hatch together: in this case, they form a great circular cavity, the eldest couple lay their eggs in the centre, and the others make a regular disposition of theirs around them. Thus, if there are four younger couples, they occupy the four angles of a square. When the laying is finished, the eggs are pushed towards the centre, but not mixed; and when the eldest delim begins to sit, all the rest take their places where their eggs have been laid, the females observing similar order. These associations are found only where the herbage is very plentiful, and they are understood always to be family groups, the centre couple being the parents of the rest. The younger birds lay fewer and smaller eggs--those of one year old, for instance, have only four or five. The period of incubation is ninety days. In the case of several couples associated thus in the same nest, the sportsmen do not attempt to destroy any but the old ones; for if they were to set about making as many holes as there were ostriches, the whole company would take fright and decamp. But perhaps it is determined to leave them all in peaceable possession for the present, and rather make a prey of the brood when hatched. The watching of the nests in such cases has led to further observations. The eggs of each pair are disposed in a heap, always surmounted by a conspicuous one, which was the first laid, and has a peculiar destination. When the delim perceives that the moment of hatching has arrived, he breaks the egg which he judges most matured, and at the same time he bores with great care a small hole in the surmounting egg. This serves as the first food of the nestlings; and for this purpose, though open, it continues long without spoiling, which is the more necessary, as the delim does not break all the eggs on the same day, but only three or four, and so on, as he hears the young ones stirring within. This egg is always liquid, but whether by a provision of nature in its original composition, or through the instinct of the parent-birds in avoiding to keep it covered like the rest, is not ascertained. The young ones, having received this their first nourishment, are immediately dried in the sun, and begin to run about; in a few days they follow the parent-birds to the pastures, always returning to shelter under their wings in the nest.