1. An artificial air space was made in the narrow end of the pipped egg by separating the shell membranes from the shell. The respiratory and hatching movements of the embryo set up pressure changes within the artificial air space and these were recorded up until the moment when the chick emerged from the shell. 3. Random movements appeared to be inhibited during the period of hatching. 4. The ways in which the presence of the artificial air space might affect the embryo have been discussed.

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