Before each of these ages there is a period of incubation, or initiation: the first age begins with Abraham, but the period of initiation with the first man Adam.
The period of incubation lasts for seven weeks, and the young are covered with a whitish down until almost as large as their parents.
Their cells during the period of incubation of the symbiotic organism are abundantly supplied with starch.
The nest is a slight hollow in the ground, wonderfully inconspicuous even when deepened, as is usually the case, by incubation, and the blackspotted olive eggs (four in number) are almost invisible to the careless or untrained eye.
A parasite may be restricted during a long incubation-period, however, and rampant and destructive later (Ustilago).
Incubation, however, is so difficult a thing to determine that it is unwise to lay down any positive limit.
The instincts of nest-building, incubation and the rearing of young, though they occur later in life than those concerned in locomotion and the obtaining of food, are none the less founded on a hereditary basis, and in some respects are less rather than more liable to modification by the experience gained by the carrying out of hereditarily definite modes of procedure.
The young, which are hatched after about four weeks' incubation, look very different from the adult.
Incubation is generally from four to six days, but it has been observed as short as thirty-six hours and as long as ten days (Bombay Research Committee).
In other cases the impression is involuntary or less consciously sought, as in dreams, which, however, are sometimes induced, for purposes of divination, by the process known as incubation or temple sleep. Dreams are sometimes regarded as visits to or from gods or the souls of the dead, sometimes as signs to be interpreted symbolically by means of dream-books, which are found not only in Europe but in less cultured countries like Siam.
As incubation goes on the hollow is somewhat deepened, and perhaps some haulm is added to its edge, so that at last a very fair nest is the result.
It is polygamous, and the male performs the duty of incubation, brooding more than a score of eggs, the produce of several females - facts known to Nieremberg Rhea.
Edulis, except that there is no period of incubation within the mantle cavity of the parent in the case of these two species.
The work of building the nest, and of incubation, falls chiefly on the female, while the duty of feeding the young rests mainly with the cock bird.
As a rule no parental care is exhibited, but incubation of the developing ova within some part of the parental body, or receptacles attached to the parent, occurs in some Lamellibranchs, some Gastropods, and in Argonauta among the Cephalopods.
Carter (U.S. Marine Hospital Service) that although the incubation of the disease was 5 days, 15 to 20 days had to elapse before the "infection" of the house, and from Ross's demonstration of the part played in malaria by the Anopheles.