The respiratory system of the egg-shell of Calliphora erythrocephala

Abstract

It is shown that Calliphora eggs require an external source of oxygen during the incubation period, and that they die in de-aerated water but develop equally well in either aerated shallow water or moist air. When immersed in water the film of air held in the outer meshwork layer of the median area between the hatching lines functions as a plastron. If the plastron is completely blocked with various nontoxic substances the eggs die. If the plastron is partially blocked, the normal time for development is increased. Replacing the air in the cavities between the vertical columns of the chorion by aerated water results in a much increased incubation period. The structure of the respiratory system of the egg-shell of Calliphora has been re-examined using the techniques adopted by Wigglesworth and Beament and Hinton. A thick middle layer exists between the inner and outer meshwork layers of the median area, and aeropyles through the middle layer connect the air films on either side. The inner layer of the median area extends dorsally into each hatching fold, and there connects by an open network with the inner meshwork elsewhere. Apart from this open network in the plane of each hatching line, the inner sheet elsewhere is continuous, and air is confined to the spaces between the vertical columns as described by Hinton.