186 Chapter IV. 



more and more in the toils of their treacherous guests. 

 In the face of such facts "animal intelligence" is alto- 

 gether untenable. On the other hand, these facts 

 furnish a new argument proving the correctness of 

 our explanation of the psychic activities of animals. 



Birds which nurse the unfledged cuckoos, do not 

 behave a whit more reasonably than the ants with 

 regard to their Lomechusa-larvae. Because the young 

 cuckoo opens its bill wider, makes more noise and 

 wiggles its stumpy wings more energetically, its 

 "foster-parents" feed it with special devotedness, and 

 rather suffer their own young to starve. Moreover 

 they calmly look on, whilst the young cuckoo pushes 

 their own offspring over the edge of the nest to make 

 them fall to the ground ; indeed it has been observed, 

 that the foster-parents assist in this work. 1 Among 

 birds, too, the nursing and adopting instincts are due 

 to the very same laws of sensitive life as in ants. 

 There is no discrimination between their own off- 

 spring and that of others, no idea of "consanguinity," 

 of "parents" or "children," but everywhere we wit- 

 ness the same unreasoning dependence on instinctive 

 sense-impressions, the appropriateness of which for 

 the welfare of their own or of strange species escapes 

 the sensitive knowledge of the animal. 



This is manifest also in the care bestowed on their 

 young by the highest mammals, the apes. Just as 

 within the same species of ants eggs, larvae, and 

 pupae are a kind of international property, and are 

 therefore received and nursed also by other colonies; 

 as the eggs of eider ducks, of hens and other birds 



"Westfalens Thierleben," II, 22. 



