63 



Ca.se 232 — continued. 



Glossy Variety. Examples of this variety, whicli in addition 

 are usually colourless, thin and semi-transparent are seen among 

 others in Woodpeckers, one of which, the Green Woodpecker (15) 

 is shown. 



Porcellanous Variety. The Tinamous, Central and South 

 American Birds are good examples, the shells of which are thick, 

 opaque and so highly glazed as to have a burnished appearance. 

 Specimens of the birds may be seen in the Upper Gallery, and its 

 eggs are shown in this Case (16). 



Greasy Variety. All ducks have eggs with a greasy or oily 

 appearance, i.e.. Mallard (17), Eider Duck (18), and Merganser (19). 



Chalky-film Variety. Some eggs are covered with a chalky- 

 film, for example the Flamingo (20), Cormorant (21) and Grebe (22). 

 It is suggested that this covering serves as a protection against, 

 too much damp — Grebes for example build over water. 



Dull Variety. Many eggs are without polish or lustre, i.e., the 

 Black Guillemot (23) and Kestrel (24). 



Granulated Variety. Examples of this variety are best 

 exhibited by eggs of many of the Running Birds — Emu (25) and 

 Cassowary (25a) — but there are others such as the Guinea Fowl (26) 

 and Francolin (27), which present quite a granulated appearance. 



(b) Colouring of Eggs. — 



The pigment of birds' eggs is on the surface and is deposited 

 immediately before it is laid. Almost every shade of colour 

 is represented, and a sufficient explanation of its meaning is not 

 always forthcoming. In many instances the colour markings are un- 

 doubtedly protective. Generally speaking eggs that are laid in the open, 

 with little or no covering or the protection of a nest, have their colour 

 markings harmonising with the colour tones of their surroundings, 

 rendering them so inconspicuous that they are not seen by a casual 

 observation, i.e., the Terns (see Case 202), the Lapwing and Snipe (see 

 Case 201), the Ptarmigan and Grouse. Again it is suggested that the 

 reason of the light colour or whiteness of the eggs of many birds that 

 build in dark places, i.e., the Starling (see Case 109), the Sand Martin 

 (see Case 154), the Kingfisher (see Case 157), and the Stock Dove (see 

 Case 224) is that the eggs may be easily found by the parents, but there 

 are many exceptions to this. 



The eggs of young birds are usually not so richly coloured as 

 when the birds are in their prime, and when old age advances the 

 colours again become less brilliant. Examples are here shown 



