eggs may be spoiled. The sale of eggs tested out of the incubators has been encouraged by the dissemination of the knowledge that infertile eggs are not changed by incubation. Eggs thrown out of an incubator will be shrunken and weakened, and some of them may contain dead germs and the remains of chicks that have died after starting to develop. Such eggs may be sold for what they are, but should never be mixed with other eggs or sold as fresh. When carefully candled they should be worth ten or twelve cents a dozen.
Fertile eggs, at the time of laying, cannot be told from infertile eggs, as the germ of the chick is microscopic in size. If the egg is immediately cooled and held at a temperature below 70 degrees, the germ will not develop. At a temperature of 103 degrees, the development of the chick proceeds most rapidly. At this temperature the development is about as follows:
Twelve hours incubation: When broken in a saucer, the germ spot, visible upon all eggs, seems somewhat enlarged. Looked at with a candle such an egg cannot be distinguished from a fresh egg.
Twenty-four hours: The germ spot mottled and about the size of a dime. This egg, if not too dark shelled, can readily be detected with the candle, the germ spot causing the yolk to appear considerably darker than the yolk of a fresh egg. Such an egg is called a heavy egg or a floater.
Forty-eight hours: By this time the opaque white membrane, which surrounds the germ, has spread well over the top of the yolk, and the egg is quite dark or heavy before the light. Blood appears at about this period, but is difficult of detection by the candler, unless the germ dies and the blood ring sticks to the membrane of the egg.
Three days: The blood ring is the prominent feature and is as large as a nickel. The yolk behind the membrane has become watery.
Four days: The body of the chick becomes readily visible, and prominent radiating blood vessels are seen. The yolk is half covered with a water containing membrane.
These stages develop as given, occurring at a temperature of 103 degrees. As the temperature is lowered the rate of chick development is retarded, but at any temperature above 70, this development will proceed far enough to cause serious injury to the quality of the eggs.
For commercial use eggs may be grouped in regard to heating as follows:
(1) No heat shown. Cannot be told at the candle from fresh eggs.