STRUCTURE AND FUNCTION OF THE EGG SHELL AS RELATED TO WATER ABSORPTION BY THE EGGS OF ACHETA DOMESTICUS (L.)

Abstract

The shell of the newly laid egg of Acheta domesticus (L.) consists of the chorion, in which two layers can be distinguished: an outer exochorion, about 2.5 μ thick; and an inner endochorion, about 0.4 μ thick, which contains lipoid and a tyrosinase. At about the time water absorption begins, the endochorion breaks up, in a more or less regular way, into many small fragments; as a result, spaces are created in the endochorion, and it seems probable that it is this structural change which permits water to be absorbed by the egg. The breaking up of the endochorion appears to be due to phenolic tanning. Also at about the time water absorption begins, the newly formed serosa begins to lay down the serosal cuticle, first an outer lipoid layer, about 0.4 μ thick, which contains a tyrosinase; and then an inner layer, which is laid down continuously while the serosa exists, and which reaches, at the time water absorption ends, a maximum thickness of 8–10 μ. Thereafter the inner layer of the serosal cuticle is steadily resorbed up to the time the egg is hatched, and the vacated shell consists only of the chorion and the lipoid layer of the serosal cuticle. Water absorption appears to be brought to an end by the phenolic tanning of the lipoid layer of the serosal cuticle.