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colour its eggs, just as it is to understand how the colouring of the hairs 

 on a Sloth changes when the leaves of the forest change. But animals do 

 know when and how to arrange themselves so as to avoid detection. 

 What is the utility of these things ? Why, for instance, are the eggs of 

 many birds white ? It is to enable them to be seen in the dark. Besides 

 being white, some eggs have a shiny surface, which reflects the light to a 

 gieat extent. Of such a character are the Wood|)ecker's and Kingfisher's 

 eggs, and they are laid in holes. It is convenient for the birds to have 

 light-giving objects in their nests. In the case of Ducks, which build 

 nests in dark places, the eggs are of that china whiteness which is not 

 found in the eggs of other Ducks. The female Sheldrake has no power of 

 concealment in itself, and so it builds its nest in a rabbit-hole, and it is 

 necessary that the eggs should be white, so that the bird may see them as 

 it walks down the hole. The Starling, again, frequently' builds its nest in 

 holes, and although the egg is of a bluish tinge, it has a bright surface, 

 and is easily seen in the dark. The egg of the Golden Eagle is a 

 conspicuous object, and it is obvious the Eagle does not care whether it is 

 protected or not. First of all, there is the precipice to deal with before 

 the Eagle's nest can be reached ; and secondly, there is the ferocity of the 

 bird. The colouring of the Guillemot's eggs seems to be i-idiculous so far 

 as its protection is concerned. Guillemots lay their eggs on the shelves of 

 rocks on precipices, and it might be said that they were pretty safe on 

 account of the safety accorded to the Gull's eggs. Bat this is not so in 

 the least. On the first appearance of danger the Guillemot leaves its eggs 

 to take care of themselves. But the shape of the eggs is such that to 

 some extent they can do that. Jackdaws and Gulls are constantly 

 seeking the eggs of the Guillemot, and it is rather a curious circiunstance 

 that at a distance of say 200 feet the eggs are hardly discernible with tlie 

 unaided sight. Mr. Hewetson gave a case where he was only able to see 

 two eggs of the Guillemot distinctly on a ledge of rock some distance down 

 a cliff. A man went to get these and found 26 others on the ledge. The 

 eggs were of various colours, and when he came to study the reason why 

 he was only able to see two of them, he realised that it was because of the 

 effect which colours .seen at a distance have on the retina of the eye. The 

 first impre.ssion, and the right one, of colours seen from a distance is soon 

 lost. The complementary colours take the place of those originally seen. 

 Guillemot's eggs are coloured so as to imitate the tints given to the sea by 

 the atmosphere, and the eye of the observer was thus deceived. 



Mr. Hewetson, in conclusion, stated that he had only touched the 

 fringe of his subject, any branch of which might be made the basis of a 

 whole lecture. 



