1. The histochemistry and ultrastructure of pheasant eggs were compared on the basis of blue or brown shell colour. 2. Differences in lectin histochemistry of the outer shell membrane calcification surface indicate a biochemical disruption of the calcification sites in blue eggs. 3. Significant differences were observed in all aspects of eggshell ultrastructure with blue eggs having thinner shells with structural defects. 4. Poor hatchability of blue eggs may reflect high rates of weight loss associated with a defective eggshell.

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The ultrastructure of the eggshell of the domestic hen has been well researched and structural studies of other avian species, such as the ostrich, often base their interpretation of egg shell structure on that of the chicken. In the ostrich, lowered hatchability and hatching trauma may be due to shell ultrastructural abnormalities. In the present study the ultrastructure of the calcified portion, and the outer shell membrane (OSM), of domesticated ostrich eggshells was investigated using standard electron microscopic techniques. Transmission and scanning electron microscopy studies demonstrated intimate contact between cup-shaped structures present on the OSMand the mammillary layer of the calcified portion of the shell. The initial calcium carbonate growth of the calcified shell was of a dendritic nature with nucleation sites on the surface of the cup's contents. The dendritic growth gave way to a more randomly-orientated, smaller crystallite growth structure, which changed in formas it neared the vertical crystal layer (VCL). The VCL is described as being both amorphous and 'crumbly' depending on the plane of fracture. These observations suggest that firstly, initial calcification is contained within the cups and is then directed outwards to formthe shell and that secondly, the VCL may contain an evolutionary, calcified cuticular layer. These observations serve as a baseline for studies investigating the effect of shell structure and strength on hatchling trauma and the influence of maternal diet

We have examined hair bulb and skin melanocytes of rufous albinos from Southern Africa to further characterize this form of albinism. In the skin melanocytes we find both eumelanosomes and pheomelanosomes at various stages of melanization and, in addition, there appeared to be many aberrant incompletely melanized melanosomes. On average, rufous melanosomes are 30% smaller than normal black skin melanosomes. In the keratinocytes, the melanosomes are packaged into distinct aggregations, whereas in normal black skin, they occur singly. We suggest that the reddish skin color of these albinos is a consequence of an increase in the pheomelanin synthesis resulting in a raised pheomelanin/eumelanin ratio and that the aggregation of melanosomes results in a skin color slightly lighter than normal. In hair bulb melanocytes, only eumelanosomes were seen and these were mostly incompletely melanized. These findings correlate with our visual observations that the hair color of Southern African albinos is very pale (light brown or ginger). Based on our observations, we speculate on the possible cause of rufous albinism.

The organic component of the avian eggshell can be divided into 3 portions, the shell membranes, the matrix and the cuticle. These have been well characterised in the chicken but little has been published with regard to the ostrich (<em>Struthio camelus</em>). A number of recent studies have indicated that the cause of intra-shell embryonic deaths in the ostrich is similar to intra-shell embryonic deaths that occur in the chicken. These deaths in the chicken are associated with the loss of or damage to the waxy cuticle and other organic components of the eggshell, which is reported to be absent in the ostrich eggshell. In this study, preliminary morphological and histochemical analyses, at the level of the light and electron microscope, have characterised the various organic components of the ostrich eggshell. The results of the histochemical and electron microscopical analyses suggest that there mayonly be 1 shell membrane in this species, which could play a major role in the limitation of bacterial penetration to the embryonic chamber. The shell membrane has a distinct elemental profile as determined by EDSanalysis. The matrix is shown to decrease in mesh size from the mammillary layer to the vertical crystal layer. The closer packing of the mesh may indicate the presence of a morphologically discernible termination signal to calcification or the remnants of an evolutionary calcified cuticle. The matrix of the pores may also forma defensive barrier against bacterial invasion, which could be damaged as a result of dipping the eggs before incubation