Avian embryos develop within the confines of an eggshell independent of maternal physiological functions. The eggshell provides not only an airway for diffusive gas exchange of the embryo, but also a wide space available for measurements of physiological functions and makes it possible to regulate directly external nvironments for physiological study. Firstly, in materials and methods section are shown measurements of various cardiogenic and electrical signals while maintaining dequate gas exchange through the eggshell. Secondly, the report summarizes mainly our studies on embryonic gas exchange and measurements of circulatory variables with an emphasis on the embryonic heart rate which we measured taking advantage of the hard eggshell. Lastly, development of thermoregulatory competence in avian embryos is briefly summarized.
