CONTENTS 3d 



PAGE 



posed incompetence of natural selection to account for the incipient 

 stages of useful structures — Causes which interfere with the ac- 

 quisition through natural selection of useful structures — Grada- 

 tions of structure with changed functions — Widely different organs 

 in members of the same class, developed from one and the same 

 source — Reasons for disbelieving in great and abrupt modifica- 

 tions 171 



CHAPTER VIII 



INSTINCT 



Instincts comparable with habits, but different in their origin — In- 

 stincts graduated — Aphides and ants — Instincts variable — Domes- 

 tic instincts, their origin — Natural instincts of the cuckoo, molo- 

 thrus, ostrich and parasitic bees — Slave-making ants — Hive-bee, 

 its cell-making instinct — Changes of instinct and structure not 

 necessarily simultaneous — Difficulties of the theory of the Natural 

 Selection of instincts — Neuter or sterile insects — Summary . . 208 



(Continued in Volume II) 



