Answer:

It may be done more or less satisfactorily if there is no way to avoid it, but better results will be obtained if some
attention is paid to the selection of eggs having shells of about the same thickness.

For instance, the eggs of all the American breeds are about the same, but in the Mediterranean and Asiatic breeds there is a wide difference in the thickness of the shells.

The shell of the Leghorn egg is thinner than that of the Brahma egg, and there will be a difference of several hours usually in the period of incubation of the eggs from these two breeds.

The best results will be secured by selecting eggs of one breed and of uniform size,