1. From the results of calcium and phosphorus balances on laying pullets, it is shown that the pullets displayed a diminution of the calcium and phosphorus in their droppings over a period of about 2–3 weeks before laying, and a correspondingly increasing retention of these elements.
2. Egg laying was correlated with a relatively heavy voiding of phosphorus in the droppings, involving a temporary negative phosphorus balance. This confirms and amplifies the results of other workers on this subject. The nature and meaning of the phenomenon are discussed.