In the bird, the egg, fertilized or unfertilized, passes out of the body and, being of conspicuous size, is readily observed. The size of the egg is due to the supply of food material which is comparable with that supplied to the mammalian young during its stay in the mother's womb. The reptiles lay eggs that are left to develop outside of the body of the mother, subject to the vicissitudes of the environment. The young of the bird, being warm blooded, cannot develop without more uniform temperature than weather conditions ordinarily supply. This heat is supplied by the instinctive brooding habit of the mother bird. Fertility of Eggs In a state of nature the number of eggs laid by wild fowl are only as many as can be covered by the female. These are laid in the spring of the year, and one copulation of the male bird is sufficient to fertilize the entire clutch. Under domestication, the hen lays quite indefinitely, and is served by the male at frequent intervals. The fertilizing power of the male bird extends over a period of about 15 days. For most of my readers, it will be unnecessary to state that the male has no influence upon the other offspring than those which he actually fertilizes within this period. The belief in the influence of the first male upon the later hatches by another male is simply a superstition. The domestic chicken is decidedly polygamous. The common rule is one male to 12 or 15 hens. I have had equally good results, however, with one male to 20 hens. In the Little Compton and South Shore districts, one male is used for thirty or even forty hens. By infertile eggs is meant eggs in which the sperm cell has never united with the ovum. Such eggs may occur in a flock from the absence of the male, from his disinclination or physical inability to serve the hens, from the weakness or lack of vitality in the sperm cells, from his neglect of a particular hen, from lifelessness, or lack of vitality in the ovule, or from chance misses, by which some eggs fail to be reached by the sperm cells. In practice, lack of sexual inclination in a vigorous looking rooster is very rare indeed. The more likely explanation is that he neglects some hens, or that the eggs are fertilized, but the germs die before incubation begins, or in the early stages of that process. The former trouble may be avoided by having a relay of roosters and shutting each one up part of the time. The latter difficulty will be diminished by setting the egg as fresh as possible, meanwhile storing them in a cool place. The other factors to be considered in getting fertile eggs, are so nearly synonymous with the problems of health and vitality in laying stock generally, that to discuss it here would be but a repetition of ideas.