The effects of cooling the egg on the respiratory movements of the hatching duck (Anas platyrhynchos).

1. The ambient temperature of pipped eggs of the domestic duck was reduced from 39 degrees C to 24 +/- 1.5 degrees C for a period of 1 hr. 2. In the majority of embryos there was a notable increase in the amplitude of respiration. 3. The respiratory frequency of each embryo fell, but remained above a value of 60 breaths/min. 4. When the eggs were rewarmed there was a reduction in the respiratory amplitude within a period of 10 min and the respiratory frequencies of the majority of embryos returned to normal within a period of 30 min. 5. These results are compared with those obtained previously in similar studies on the domestic fowl and quail.