Chap. VIIL] LNSTINCT. 319 



CHAPTER Vin. 



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 develop- 

 ment will probably appear to the reader a difficulty suffi- 

 cient to overthrow my whole theory. I may here pre- 

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

 mental powers, any more than I have with that of life it- 

 self. "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 ac- 

 tions are commonly embraced by this term; but every 

 one understands what is meant, when it is said that in- 

 stinct impels the cuckoo to migrate and to lay her eggs 

 in other birds' nests. An action, which we ourselves re- 

 quire experience to enable us to perform, when per- 

 formed 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 



