Abstract AT THE conclusion of egg shape inheritance studies reported by Marble (1943) there were available Barred Plymouth Rock hens from selected family lines that laid eggs having a wide spread in egg shape index. This population was used for a study of the physical and physiological factors influencing egg shape. Consideration was first given to the possible effect of the character of the albumen on egg shape. Data collected for this study are presented in this paper. A second paper will include results of a study of the muscular structure of the oviduct and a detailed study of that portion of the oviduct involved in establishing egg shape. REVIEW OF LITERATURE Scott (1938) points out a straight line relationship existing between size of yolk and amount of white secreted in a given oviduct when yolks of smaller than mature size for the given hen were substituted. He also demonstrated that . . .