Correlation of birth weight and crown-rump to the number of implantations and litter size in rabbits.

The empirical coefficient of correlation and the empirical coefficient of regression were evaluated in New Zealand White rabbits between birth weight and crown-rump on the one hand and number of implantations and litter size on the other. The average birth weight decreases with increasing litter size (P = 0.01). The decreased supply of blood to the single fetus in big litters might be responsible for this result. As no definite correlation between crown-rump and litter size could be proved, the conclusion may be drawn that the crown-rump is more determined by genetic factors than is the birth weight.