CONTENTS 



Chapter IV 



The Effect of Light on Pigmentation 



The Types of Colour Change 

 Mechanism of Colour Changes 



Chromatophores . 



Types of Pigment 



Types of Response 



Primary, 89 ; Secondary, 91 ; Indirect, 92 

 Central Organization of Pigmentary Changes, Nervous and Hormonal 



Chapter V 

 The Emergence of Vision 

 Light -sensitiveness, the Light Sense and Vision .... 



PAGE 



82 

 85 

 85 

 87 

 89 



92 



102 



Part II. The Evolution o! the Visual Apparatus 



Chapter VI 

 The Morphology of Invertebrate Eyes 



I. The Genesis of the Eye .... 



Dermal Photosensitivity. 

 Specific Light-sensitive Cells . 



Pigments ..... 



Melanin, 118 ; Visual Pigments, 118 



Ommochromes, 122 



II. The Structure of Invertebrate Eyes 



1. Eye-spots : Stigmata 



2. Light-sensitive Cells . 



3. The Simple Eye 



(a) The Unicellular Eye . 

 (6) The Multicellular Simple Eye 

 (i) The Subepithelial Eye 

 (ii) The Epithelial Invaginated Eye 



The Flat Eye, 136; the Cupulate Eye, 137; the 

 Vesicular Eye, 141 

 (iii) The Inverted Retina 



(c) Aggregate Eyes ..... 



(d) Composite Ocelli ..... 



4. The Compound Eye ...... 



(a) The Development of Ocelli and Compound Eyes 

 (6) The Structure of the Compound Eye . 



The Simple Ommatidial Eye, 159 ; the Composite Com 



pound Eye, 160 

 (i) The Compound Eyes of Arachnids 

 (ii) The Compound Eyes of Crustaceans 

 (iii) The Compound Eyes of Insects 

 (c) The Optical System of the Compound Eye 



The Appositional Eye, 173 ; the Superpositional Eye, 

 174 ; the Analysis of Polarized Light, 174 



113 

 114 

 115 

 117 



126 

 125 

 127 

 129 

 130 

 132 

 132 

 135 



146 

 151 

 152 

 154 

 156 

 157 



160 

 163 

 166 

 170 



