The Structure of the Insect Egg-Shell in Relation to the Respiration of the Embryo

1. The site of gaseous exchange in the eggs of Rhodnius prolixus (Stahl) is shown to be the rim of the cap which covers the anterior end of the egg. Most of the oxygen consumed by the embryo enters the egg through the micropyles and pseudomicropyles which penetrate the shell in this region. 2. The physical conditions necessary for the passage of sufficient oxygen through these pores is discussed. A continuous gas space under the shell--the presence of which can be deduced on theoretical grounds--is shown to exist in the Rhodnius egg. 3. The relationship between waterproofing and the permeability of the shell to oxygen is discussed.