The hen's egg: Incidence and inheritance of some egg abnormalities

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Abstract
1. More than 9000 eggs, each laid by a known hen, were examined and malformations of six types recorded: double‐yolked, A, B, rough, shell‐less and thin‐shelled. 2. A and B malformations are those seen in, respectively, an egg that is held in the shell gland for an abnormally long period and one that reaches the shell gland while an A‐egg is still there; many of the eggs recorded as rough‐shelled were probably A‐eggs for which the corresponding B‐eggs had been lost. 3. The birds were of three strains: a medium‐body‐weight brown‐egg‐laying strain and a White Leghorn strain, both of commercial origin, and a laboratory strain of Brown Leghorns. 4. The incidences of egg malformation in the three strains were 8.3, 9.2 and 0.5%. 5. A‐, B‐ and rough‐shelled eggs constituted more than two‐thirds of all malformed eggs. 6. Evidence from two generations suggests that these malformations have a high heritability.