Genetic Variation in 14-Day Chick Embryo Weight

INVESTIGATIONS of the causes of variation in chick embryo weight have been numerous. Until recently, however, the effects of heredity on embryo weight have not been demonstrated. Blunn and Gregory (1935) and Krzanowska (1959) concluded that egg weight did not influence embryo weight. Byerly (1932), McNally and Byerly (1936), and Byerly et al. (1938), observed that egg weight did influence embryo weight while Bray and Iton (1962) and Coleman et al. (1964) found egg weight to significantly affect embryo weight. Henderson (1930) and Blunn and Gregory (1935) found neither breed nor strain differences to be shown by embryo weight. Byerly et al. (1938) concluded that embryos from two breeds and hybrid embryos in eggs from each breed grew at similar rates. Bray and Iton (1962), however, reported a significant strain effect on embryo weight. McNary (1960) in inbred lines and their crosses found significant differences in embryo weight at 7…