FROM THE PREFACE: Dramatic changes occur in the physiology of most animals during their development. Among the vertebrates, birds are entirely oviparous, live for variable periods in a cleidoic egg, and show fundamental alterations in excretion, nutrition, and respiration at the time of hatching. In contrast, the eutherian mammals are all viviparous, depend on the maternal circulation and a specialized placenta to provide food, exchange gases, and...
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