viii CONTENTS. 



CHAPTER VIIL 



INSTIN'CT. 



Instincts comparable with habits, but different in their origin- 

 Instincts graduated — Aphides and ants — Instincts variable — 

 Domestic instincts, their origin — Natural instincts of the 

 cuckoo, Molothrus, 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 Page 319 



