ABSTRACT
Two series of observations were made to determine the time and amount of loss of eggs in relation to the number shed per ovary and per mouse.
The correlations between sides within mice for eggs shed was −0·528, for corpora lutea counts −0·436, for implantations −0·300, and for live embryos −0·111.
A positive linear trend of loss of fertilized eggs with increasing numbers of eggs per uterine horn has been shown to occur before implantation.
Possible causative mechanisms for the loss are discussed in relation to observations on embryonic mortality previously reported by other workers.
We wish to express our gratitude to Prof. C. H. Waddington for laboratory facilities, to Dr D. S. Falconer for much helpful criticism and advice and to Dr B. Woolf for statistical advice. J. C. Bowman gratefully acknowledges financial support from the Agricultural Research Council.
