Dirty eggs are grouped roughly in three classes: (A) Plain dirties, those to which soil or dung adheres; (B) stained eggs, those caused by contact with damp straw or other material which discolors the shell (plain dirties when washed usually show this appearance); (C) smeared eggs, those covered with the contents of broken eggs. For the first two classes of dirty eggs the producer is to blame. The third class originates all along the route from the nest to consumer. The percentage of dirty eggs varies with the season and weather conditions, being noticeably increased during rainy weather. In grading, about five per cent. of farm grown eggs are thrown out as dirties. These dirties are sold at a loss of at least twenty per cent. The common trade name for cracked eggs is checks. Blind checks are those in which the break in the shell is not readily observable. They are detected with the aid of the candle, or by sounding, which consists of clicking the eggs together. Dents are checks in which the egg shell is pushed in without rupturing the membrane. Leakers have lost part of the contents and are not only an entire loss themselves, but produce smeared eggs. The loss from breakage varies considerably with the amount of handling in the process of marketing. A western produce house, collecting from grocers by local freight will record from four to seven per cent. of checks. With properly handled eggs the loss through breakage should not run over one or two per cent. Eggs in which the chick has begun to develop are spoken of as "heated" eggs. Infertile eggs cannot heat because the germ has not been fertilized and can make no growth. That such infertile eggs cannot spoil is, however, a mistaken notion, for they are subjected to all the other factors by which 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.