The Effects of Breed on Growth of the Embryo in Fowls and Rabbits

Abstract

A critical discussion of the, observations of Byerly (See B. A. 6(2) : Entry 5379) on the effects of breed on growth rate of the embryo previous to hatching in Rhode Island Red and White Leghorn fowls and in their hybrids. Byerly''s data show (1) that the embryos of the larger breed have a more rapid growth rate, though the absolute weight attained at hatching is limited by the size of the egg, and (2) that hybrid embryos produced by crossing the 2 breeds grow faster than pure bred embryos of either breed. These conclusions are in harmony with those reached by Castle and Gregory in their studies of the embryonic development of large and of; small races of rabbits, and of their hybrids.