A comparative study of changes in the fine structure of avian eggshells during incubation

A scanning electron microscope study of the morphological changes which occur in shells of hen and quail eggs during incubation is described. The results are compared with observations on the shells of hatched eggs taken from a range of species. It was found that less change occurred in the shells of altricial species than precocial ones, the difference being associated presumably with a smaller calcium requirement for developing altricial embryos. The cores rather than the sides of mammillae appeared to be the major sites of erosion.