xiv ANIMAL LIFE 



fat independently of the food The original mode of 

 nutrition in animals a double one (a) by photosynthesis ; 

 (6) by elaboration of solid organic food The fatty pig- 

 ments in animals are a vestige of the first mechanism 

 \\luch has been supplanted by the second and more 

 efficient one Pigments arising through elimination of 

 waste substances from the tissues and their deposition in 

 the skin The white colour of butterflies. Summary : 

 pigments originally nutritive or respiratory ; excretory 

 pigments a by-product of vital activity The original 

 function may be lost and a decorative meaning and use 



gained secondarily 160 



2. The secondary meanings of animal colours : 



Harmony between animals and their surroundings the 

 note of animal life Sympathetic colouration a case of 

 such harmonious adaptation Instances of colour-sym- 

 pathy ; the JEsop prawn The development of colour- 

 sympathy in the life of the prawn Critical period in its 

 career The abundance of similar sympathetic colouration 

 in other marine animals Scarcity of such in fresh-water 

 Colour sympathy in land-animals Arctic and desert 

 colouration Forest and field renderings of background 

 and foliage on the skins of animals Effacive gradation 

 in the shading of the skin Cryptic colouring, form, and 

 posture amongst stick-caterpillars, moths, and butterflies 

 The leaf-butterfly and Mantis of India Spiders 

 Mimetic resemblance of certain unrelated butterflies 

 Seasonal differences of colouration and habit Protective 

 meaning of cryptic colouring Experiments on cater- 

 pillars and mantises Warning colouring associated with 

 distastefulness The pigments of animals older than the 

 effect they produce 167 



CHAPTER IX 



THE WELFARE OF THE RACE 



Racial welfare a stimulus to which all beings respond Personal 

 acquisitions of racial value The heritage of animals and of 

 man The response of animals to the stimulus of racial 

 welfare The stringency of the test by which the value 

 of this response is measured The ornaments of sex 



