216 MENTAL EVOLUTION IN ANIMALS. 



was not blind to the unnatural character of her brood, is proved 

 by the fact of her having adapted her actions to their pecu- 

 liar requirements. But to test the degree to which such 

 adaptation might go, I tried the experiment of selecting the 

 two most diverse kinds of animals I could think of, and givins: 

 the young of the one to be reared as foster-children by the 

 other. The animals which I selected for this purpose were a 

 ferret and a hen. The following was the result of the experi- 

 ment as published at the time in " Nature."* 



" A bitch ferret strangled herself by trying to squeeze 

 through too narrow an opening. She left a very young 

 family of three orphans. These I gave, in the middle of the 

 day, to a Brahma hen, which had been sitting on dummies 

 for about a month. She took to them almost immediately, 

 and remained with them for rather more than a fortnight, at 

 the end of which time I had to cause a separation, in conse- 

 quence of the hen having suffocated one of the ferrets by 

 standing on its neck. During the whole of the time that the 

 ferrets were left ivith the hen, the latter had to sit upon the nest ; 

 for the young ferrets, of course, were not able to follow the 

 hen about as young chickens would have done, in accordance 

 with the strong instinct of following with which Mr. Spalding 

 has shown young chickens to be endowed. The hen, as 

 might be expected, was very much puzzled at the lethargy of 

 her offspring. Two or three times a day she used to fly ofl" 

 the nest, calling upon her brood to follow ; but, on hearing 

 their cries of distress from cold, she always returned imme- 

 diately and sat with patience for six or seven hours more. It 

 only took the hen one day to learn the meaning of these 

 cries of distress ; for after the first day she would always run 

 in an agitated manner to any place where I concealed the 

 ferrets, provided that this place was not too far away from 

 the nest to prevent her from hearing the cries of distress. 

 Yet I do not think it would be possible to conceive of a 

 greater contrast than that between the shrill piping note of a 

 young chicken and the hoarse growling noise of a young 

 ferret. On the other hand, I cannot say tliat the young 

 ferrets ever seemed to learn the meaning of the hen's cluck- 

 ing. During the whole of the time that the hen was allowed 

 to sit upon the ferrets she used to comb out their hair with 

 her bill, in the same way as hens in general comb out the 



* VoL xi, p. 553. 



