Abstract
1. The genetic portion of the variance in birth weight of Corriedale Breed in the Takikawa Sheep Breeding Station is estimated 32 percent, the portion of variance arising from differences in tangible environment is 26 per cent, while 42 per cent arises from intangible environment or accidents of development. 2.The sex difference in birth weight is real but camparatively unimportant among the other causes of differences in birth weight. 3. The effect of the litter size on birth weight is comparatively large and f.he heritability of the litter size is 34 per cent. Hence, the differences of litter size are caused mostly by differences in the environrnent such as " Flushing " 4. The yearly difference in birth weight is not found.
