COLORATION AFFECTED BY THE ENVIRONMENT. O/ 



thrushes and other snail-eating birds on the Lower Rhine than 

 at Bonn, or cice ct-rsa if the "citron yellow' variety is the 

 more conspicuous. 



The suffusion of the markings and the duller colour which is 

 said to occur among Alpine butterflies is in striking contrast 

 with the unusual brilliancy of colour which is noticeable in 

 Alpine plants. 



The latter change is said to be owing to the less numbers of 

 insects which cross-fertilise the flowers; and hence the need for 

 a greater effort, so to speak, on the part of the plant to attract 

 them and thus secure the desirable effects of their visitations. 



This might be urged as an objection to the climatic 

 influence, on the grounds of unlike effects in the two cases. 

 But it is perhaps hardly necessary to point out that the 

 pigments of the butterflies' wings are different from those of 

 the flowers, and that the physiological processes which take 

 place in the bodies of animals without chlorophyll are in the 

 first place different from those of chlorophyll-bearing plants, 

 .and in the second place the same conditions may produce 

 different effects. 



Examples of Melanic Varieties found upon Islands. 



There are a good many other examples of a tendency towards 

 melanism more or less realised among the inhabitants of 

 islands. 



The Galapagos Islands consist of a group of islands, of 

 various areas, situated some five hundred miles to the west 

 of the South American continent. One of the most charac- 

 teristic inhabitants of these islands is the curious marine 

 Iguanoid lizard, Oreocephalus. It is thus described by 

 Darwin : "It is a hideous-looking creature, of a dirty black 

 colour, stupid and sluggish in its movements. The usual 



