26 COLOUR IN NATURE chap. 



purple from various small shell-fish, such as Murex 

 and Purpura, while the different preparations of 

 carmine and cochineal, saffron, and haematoxylin or 

 logwood are other familiar examples of pigments 

 produced by animals or plants which are habitually 

 employed as colouring-agents. The greater number 

 of the pigments of plants and animals are, however, 

 too fugitive to be so utilised, and in consequence are 

 in their pure state unfamiliar to most people. Such 

 are chlorophyll itself, the blue, red, orange and 

 yellow pigments of flowers, and the green, red, 

 yellow and orange pigments of animals, most of 

 which are destroyed by light or other agents with 

 great rapidity. It is indeed worth noting that most 

 of the natural dyes are of vegetable origin, and that 

 they are usually inconspicuous and apparently unim- 

 portant during the life of the plant, cf haema- 

 toxylin, brasilin, etc. So, too, when they are of 

 animal origin, they are not usually important in 

 producing the coloration of the living creature, cf. 

 Murex, the coccus insect, etc. It is partly in con- 

 sequence of the fact that the pigments important 

 in producing coloration are so fugitive and so 

 diiificult to obtain in a pure state, that so little is 

 really known of their relations and constitution. 

 Many of them, indeed, have hardly been investigated 

 at all. 



We may note here a point which will be dwelt 

 on in detail in its proper place, that a pigment 

 found in an animal need not necessarily be formed 

 by that animal. There are some instances of 

 pigments which are transferred from one animal 

 or plant to the tissues of another by the food with 



