xiv ANIMAL LIFE 



PAGE 



fat independently of the food — The original mode of 

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

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

 ments in animals are a vestige of the first mechanism 

 which has been supplanted by the second ami 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 



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 .Esop 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 

 distaste-fulness — 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 ol the test by which the value 

 of this response is measured — The ornaments ol sex 



