Abstract
The shell membrane of a Chinese soft-shelled turtle egg acts as a bag enclosing egg white and water. The main body of the shell membrane is a meshwork of fibers, and is organized into an inner and an outer membrane. The limiting membrane demarcates the shell membrane at the interface with the egg white. Transmission electron microscopy revealed that the limiting membrane has a width of 362nm and consists of dense materials. There were many canals that run perpendicularly or obliquely to the plane of the membrane. Scanning electron microscopy showed many holes, 20nm in size, on the inner surface of the membrane. The water permeability of the shell membrane was 5nl/mm2 per min. Neither the ultrastructure nor water permeability changed throughout the incubation period of 54 days. No significant difference was observed between membranes of the embryonic side and yolk side of individual eggs. These results are compared with those of corresponding observations of avian eggs.
