Chap, yhl] instinct. 319 



CHAPTER VIIL 



Instinct. 



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. 



Many instincts are so wonderful that their development 

 will probably appear to the reader a difficulty sufficient 

 to overthrow my whole theory. I may here premise, 

 that I have nothing to do with the origin of the mental 

 powers, any more than I have with that of life itself. We 

 are concerned only with the diversities of instinct and of 

 the other mental faculties in animals of the same class. 

 I will not attempt any definition of instinct. It would 

 be easy to show that several distinct mental actions are 

 commonly embraced by this term ; but every one under- 

 stands what is meant, when it is said that instinct 

 impels the cuckoo to migrate and to lay her eggs in other 

 birds' nests. An action, which we ourselves require 

 experience to enable us to perform, when performed by 

 an animal, more especially by a very young one, without 

 experience, and when performed by many individuals 

 in the same way, without their knowing for what purpose 



