Kale is one of the very best crops for soiling purposes. It is planted in the fall and fed by pulling off the lower leaves during the winter. In the spring the hardened stalks stand at a considerable height and the field may be used for growing young chicks, giving shade, and at the same time producing abundant green feed, without any immediate labor, which means a great saving in the busy season. A set of panels or netting stretched on light frames is provided. They are of sufficient number to set along the longest side of one of the fields. A strip along the fence, four or five feet wide, can be planted to sunflowers, corn, rape, kale, or other rank growing crop and the panels leaned against the fence to protect the young plants from the hens. In this way the fence rows can be kept provided with the shade of growing crops, which relieves the otherwise serious fault of this plan of poultry farming, in that the hens would be required to live in absolutely barren and sunburned lots, for we propose to keep five or six hundred hens on one and a half acres of ground, and no green things could get a start without protection. Rotate the houses from field to field as often as the crops allow. Never permit hens to run in one bare field for more than six months at a time. Always keep every inch of ground not in use by the chickens, luxuriant in something green. If you have a crop of vegetables which are about matured, drill rape or crimson clover between the rows; by the time the crop is harvested and the hens are to be moved in, such crops will have made a good growth. The hens will kill it out but it will be a "profitable killing." By this system of intensive combination of trucking and poultry farming, we have a combination which for small capital and small lands cannot be beaten. The hens should yield better than a dollar profit per head on this plan; the one and a half acres automatically fertilized and intensely cultivated, growing two or three crops a year, should easily double the income. Twelve hundred dollars a year is a conservative estimate for the net income from such a plant, and the original investment, exclusive of residence, will not be over one thousand dollars. CHAPTER VI INCUBATION The differences in the process of reproduction in birds and mammals is frequently misunderstood. The laying of the bird's egg is not analogous to the birth of young in mammals. The female, whether bird or beast, forms a true egg which must be fertilized by the male sperm cell before the offspring can develop. In the mammal, if fertilization does not occur, the egg which is inconspicuous, passes out of the body and is lost. If fertilized, it passes into the womb where the young develops through the embryonic stages, being supplied with nourishment and oxygen directly by the mother.