MENTAL FACULTIES 



cession like other birds, and cannot incubate like these. Its 

 ancestors, therefore, not accidentally, but from reflection, laid 

 their eggs in other birds' nests, and this habit has now 

 perhaps become instinctive, but is also doubtless maintained 

 by the effects of experience, in that the young cuckoos know 

 the characteristics of their foster-parents' nest, but have never 

 learnt to build a nest, and have inherited no instinct of 

 nidification from their parents. 



There are vagabonds in human society, in the lowest as well 

 as the highest, who lead in all respects a cuckoo's life our 

 knowledge of these enables us better to understand the 

 instinct of the cuckoo. Such people trouble themselves no 

 more than the cuckoo about their offspring, but let others 

 look after them, and even leave them at other people's doors, 

 or at the door of the foundling hospital. 



But it is extremely remarkable that the cuckoo has still so 

 far retained the instinct of providing for its offspring in spite 

 of its pleasure-seeking life, that it secures the maintenance 

 of the species although the instinct of incubation has been 

 entirely lost. Compare with this again the habits of our 

 domestic fowls. In them the incubating instinct is obviously 

 gradually being lost; it occurs only in a few individual 

 hens. Most hens are indifferent to the fate of the eggs they 

 lay, or even, like the domestic duck, simply let them drop 

 anywhere. Domestic ducks, like domestic hens, have for- 

 gotten how to build a nest, like the cuckoo. But the original 

 form of the domestic duck (Anas boschas) makes a nest in 

 which she lays eight to sixteen eggs. The original of the 

 domestic fowl (Gallus bankiva) in India also lays in a nest, 

 only roughly prepared it is true, eight to twelve eggs, and, like 

 the wild duck, lays them in rapid succession, so that they 

 are hatched all together. 



The difference in the persistence of the parental instinct 

 in domestic fowls and ducks on one hand, and in the cuckoo 



