Hatchability as Related to Seasons and Hour of Laying

P in hatchability have been studied by a large number of workers including Pearl, Dunn, Hutt, Jull, Warren, Waters, Byerly and Dove as well as many others, reported in Jull's Poultry Breeding, 1932. Under uniform conditions of incubation, the greater proportion of evidence indicates that the genetic makeup of the female and of her mate largely determine the percentage of fertile eggs that will hatch. Malposition and a few lethal genes are known to increase embryonic mortality. Byerly, Knox and Jull (1934) express the opinion that the inheritance of hatchability must be determined by a very large number of genes. Recently Dove (1935) and Waters (193S) have demonstrated that the lethal effects of malposition have probably been exaggerated. Both of these workers have shown that normal chicks assume these socalled abnormal positions as a phase of normal development between the eighteenth day and the hatching day. In view of this fact both workers conclude that many dead chicks that are found abnormally oriented in the egg have died at a particular stage in