birds' nests and eggs. 139 



Many birds make their nests in lofty trees, or on the ledges 

 of precipitous cliffs. Of these the Eagles, Vultures, and Crows 

 are conspicuous examples. They are, for the most part, too 

 powerful to be afraid of the marauding Magpie, and only fear 

 the attacks of beasts of prey, amongst which they doubtless 

 classify the human race. They rely for the safety of their eggs 

 on the inaccessible positions of the nest. Many of them also 

 belong to a still larger group of birds who rely for the safety 

 of their eggs upon their ability, either singly, in pairs, or in 

 colonies, to defend them against all aggressors. Few colonies 

 of birds are more interesting than those of Herons, Cormorants, 

 and their respective allies. These birds lay Avhite or nearly 

 white eggs. Nature, with her customary thrift, has lavished no 

 colour upon them because, apparently, it would have been 

 wasted effort to do so; but the eggs of the Guillemot are a 

 remarkable exception to this rule. Few eggs are more gor- 

 geously coloured, and no eggs exhibit such a variety of colour. 

 It is impossible to suppose that protective selection can have 

 produced colours so conspicuous on the white ledges of the 

 chalk cliffs ; and sexual selection must have been equally power- 

 less. It would be too ludicrous a suggestion to suppose that 

 a cock Guillemot fell in love with a plain-coloured hen because 

 he remembered that last season she laid a gay-coloured egg. 

 It cannot be accident that causes the Guillemot's eggs to be so 

 handsome and so varied. In the case of birds breeding in holes 

 secure from the prying eyes of the marauding Magpie, no colour 

 is wasted where it is not wanted. 



The more deeply Nature is studied, the more certain seems 

 to be the conclusion that all her endless variety is the result 

 of evolution. It seems also to be more and more certain that 

 natural selection is not the cause of evolution, but only its 

 guide. Variation is the cause of evolution, but the cause of 

 variation is unknoicn. It seems to be a mistake to call variation 

 spontaneous, fortuitous, or accidental, than which exjiressions 

 no adjectives less accurate or more misleading could be found. 

 The Athenian philosophers displayed a less unscientific attitude 

 of mind towards the Unknown when they built an altar in 

 its honour.* 



'■= Abstract of a lectm-e delivered at the London Institution. 



