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Embryogenesis of the secondary palate in pigeons.

Embryogenesis of the secondary palate in pigeons was studied, using light and electron microscopy. The secondary palate of the pigeon develops between Days 7 to 11 of incubation. During this period the palatal processes grow toward one another, but unlike those in the mammals and alligator, they never fuse. In contrast to both the chick, wherein the medial edge epithelium (MEE) differentiates to orthokeratinization, and quail wherein the MEE becomes parakeratinized, the MEE of the pigeon, like that of the duck, differentiates to a nonkeratinized, stratified squamous type. It is suggested that although patterns of morphogenesis of the secondary palate in different bird species appear to be similar, the programming, and consequently, the pattern of subcellular differentiation of the MEE may reflect natural selection or adaptation to differences in diets and feeding habits.