Transmission electron microscopy of the vertical crystal layer and cuticleof the eggshell of the domestic fowl

1. Eggshell pieces (1 cm(2)) were decalcified using a solution of EDTA (200 g/litre, pH 6.9 to 7.0) in paraformaldehyde (2 g/litre) and glutaraldehyde (0.5 g/litre) in phosphate buffer. 2. They were prepared for transmission electron microscopy (TEM). 3. TEM identified a vertically aligned matrix associated with the vertical crystal layer (VCL). It is hypothesised that the vertical orientation of ca lcite crystals in the VCL is closely linked to this vertical matrix. 4. TEM also revealed the presence of a 2-layered cuticle, the inner layer c ontaining vesicles which were absent in the outer 5. Cuticular vesicles contain hydroxyapatite and are thought to play a role in the termination of shell formation. The current paper presents data rel ating to microbial apatitic systems that strengthen this hypothesis.