TABLE OF CONTENTS xv 



5. THE CIRCULATORY SYS I KM .................. 121 



The general features of the circulatory system ...... 121 



The heart ........................ 121 



The pulsations of the heart .... 122 



The aorta ............................... 122 



The circulation of the blood .................................. 122 



Accessory circulatory organs ................................. 1 22 



6. THE BLOOD ........................ I J 2 



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 THK SKNSK-ORC.ANs . i| INSECTS.. 12() 



A classification of the sense-organs ............. .... 1 29 



The caticular part of the sense-organs ................... i 30 



10. THE ORGANS OF TOUCH .................. 13! 



II. THE ORGANS OF TASTE AM) SMELL. . .. 132 



12. THE OKI. \N^ (>K SIGH T ........ .... 134 



a. The general features ........................... . . 134 



The two types of eyes ................. 1 34 



The distinction between ocelli and compound eyes. . .... 134 



The absence of compound eyes in most of the Apterygota i 35 



The absence of compound eyes in larva; .... i 35 



b. The ocelli .............. 135 



The primary ocelli .................... 1 35 



The adaptive ocelli ............ i3'> 



The structure of a visual cell ........ 137 



The structure of a primary ocellus .... 1 37 



Ocelli of Ephemerida ......... '.v> 



r. The compound eyes ..... i.V) 



The physiology of compound eyes 14' 



The theory of mosaic vision ..... 14' 



Day-eyes ............... '4- 



Night-eyes .................... ' -U 



Eyes with double function ........ 1 4.^ 



Divided eyes ............................ 1 44 



Thetapetum.. 'It 



