TABLE OF CONTENTS xv 



5. THE CIRCULATORY SYSTEM 121 



The general features of the circulatory system 121 



The heart I2I 



The pulsations of the heart <.... 122 



The aorta 122 



The circulation of the blood 122 



Accessory circulatory organs 122 



6. THE BLOOD 122 



7. THE ADIPOSE TISSUE 123 



8. THE NERVOUS SYSTEM 123 



a. The central nervous system 123 



b. The oesophageal sympathetic nervous system 125 



c. The ventral sympathetic nervous system 127 



d. The peripheral sensory nervous system 128 



9. GENERALIZATIONS REGARDING THE SENSE-ORGANS OF INSECTS .. I2Q 



A classification of the sense-organs 129 



The cuticular part of the sense-organs 130 



IO. THE ORGANS OF TOUCH 131 



II. THE ORGANS OF TASTE AND SMELL 132 



12. THE ORGANS OF SIGHT 134 



a. The general features 134 



The two types of eyes 134 



The distinction between ocelli and compound eyes 134 



The absence of compound eyes in most of the Apterygota 135 



The absence of compound eyes in larvae 135 



b. TheocelH 135 



The primary ocelli 135 



The adaptive ocelli 136 



The structure of a visual cell 137 



The structure of a primary ocellus 137 



Ocelli of Ephemerida 139 



c. The compound eyes 139 



The physiology of compound eyes H 1 



The theory of mosaic vision I4 1 



Day-eyes I4 2 



Night-eyes X 43 



Eyes with double function I 43 



Divided eyes X 44 



The tapetum J 44 



