CONTENTS xiii 



PAGE 



ditions The origin of the eye and ear from the skin The 

 origin of the central nervous system in the skin The origin 

 of the nerves in (a) a primitive connection between the 

 central system and muscle ; and (6) an equally primitive con- 

 nection between the internal movements and the governing 

 central system ; and (c) a correlation between (a) and (6) . 140 

 The stiffening of these inward and outward responses into habit 

 and tradition The evolution of more complex responses 

 based upon a groundwork of muscular and sensitive re- 

 sponse The greater strenuousness of life on land and in 

 air has led to the evolution of complex instincts The 

 power of profiting by experience The domestication of 

 animals, and its far-reaching effects on man's social life . 144 



CHAPTER VIII 



THE COLOURS OF ANIMALS 



i . The primary meanings of animal colours : 



Colours the outcome of inward processes The relation 

 of animal pigments to light Exposed surfaces of the 

 body more deeply coloured than shaded ones Experi- 

 mental evidence on the colouring action of light The 

 bleaching effect of darkness Agreement between plant 

 foliage and animals in colour distribution The green 

 pigment of plants concerned in nourishment The red pig- 

 ment of blood and muscle a respiratory substance, and only 

 secondarily a decorative one The relation between the 

 two in chemical composition Loss of green pigment in 

 parasitic plants ; temporary loss in minute flagellate 

 organisms when supplied with organic food, reacquire- 

 ment of the green colour under inorganic nourishment^ 

 Nature of these Flagellata : a connecting-link between 

 animals and plants The adoption of solid food and the 

 origin of muscle gave the animal branch of this family 

 greater facilities for distribution and involved more efficient 

 oxidation Evolution of the blood pigments . . .149 



The evolution of red and yellow fatty pigments Wide 

 distribution of these in animals and plants Association of 

 these pigments with stores of reserve food Association 

 of fat with these pigments in the skin and other tissues 

 of the ^Esop prawn Evidence for the formation of this 



