CHAP. VIII.] INSTINCT. 191 



to believe that many structures beautifully adapted to all the 

 other parts of the same creature and to the surrounding conditions, 

 have been suddenly produced ; and of such complex and wonderful 

 co-adaptations, he will not be able to assign a shadow of an 

 explanation. He will be forced to admit that these great and 

 sudden transformations have left no trace of their action on the 

 embryo. To admit all this is, as it seems to me, to enter into the 

 realms of miracle, and to leave those of Science. 



CHAPTER VIII. 



INSTINCT. 



Instincts comparable with habits, but different in their origin .fnstincts 

 graduated Aphides and ants Instincts variable Domestic instincts, 

 their origin Natural instincts of the cuckoo, raolothrus, 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 em- 

 braced by this term ; but every one understands 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 it is performed, is usually 

 said to be instinctive. But I could show that none of these 

 characters are universal. A little dose of judgment or reason, as 

 Pierre Huber expresses it, often comes into play, even with 

 animals low in the scale of nature. 



Frederick Cuvier and several of the older metaphysicians have 

 compared instinct with habit. This comparison gives, I think, an 

 accurate notion of the frame of mind under which an instinctive 



