Lethality of Embryo Malpositions in the Domestic Fowl

APPROXIMATELY one-half of the fer-< • tile eggs which fail to hatch in any lot of eggs set contain chicks which have nearly completed development. About half of these, or one-fourth of all the fertile eggs which have failed to hatch, contain chicks in one or more of several malpositions. Thus, in a lot of eggs 60 percent of which hatch, the number of chicks affected by mal-positions is about 10 percent of the fertile eggs set. It is obviously of very great eco-nomic importance to know to what extent the several malpositions are lethal to the affected chicks. It is the object of the pres-ent paper to present new data on the lethal-ity of malpositions and to scrutinize the data and opinions found in the literature. It was supposed by Sanctuary (1925) that malposition1 I is always lethal; he stated that chicks in other malpositions sometimes hatch. Hale (1930) expressed the opinion that chicks in any malposition have little chance of hatching. Smith (1930) stated that malposition affects hatchability of eggs in Ontario at least 5 percent. Byerly (1930) was of the opinion that malpositions III and IV are of doubtful importance as barriers to hatching; that malposition I is always lethal and chicks in malposition II are often able to pip. Byerly and Olsen 1 The classification of Hutt (1929) is followed in the present paper; malposition I is head be-tween legs; malposition II, head in small end; mal-position III, beak under left wing; malposition IV, head away from air cell. Malposition V, feet over head and malposition VI, beak over right wing (cf. Hutt and Pilkey, 1934) have not been studied at Beltsville, Md. (1931, 1933) showed that chicks in mal-position II often hatch. Byerly and Olsen (1934) showed that malposition III is lethal in most cases either because of concomitant retardation or because of inability to turn the body within the shell or both. Though Hutt and his co-workers (Hutt