228 MENTAL EVOLUTION IN ANIMALS. 



being intentionally instructed by the old, but they are in- 

 structed by themselves, i.e., by their individual experience. 

 And this is, after all, the most important point, or the point 

 to which the intentional education by parents is subsidiary. 

 I shall therefore give a few more instances to show that 

 many instincts (usually those of obviously secondary origin) 

 are first manifested by young animals in an imperfect, or not 

 fully evolved condition, and afterwards become perfected in 

 the school of individual experience. Such cases stand in 

 marked antithesis to those of the congenitally perfect 

 instincts already alluded to, which have been so well investi- 

 gated by Mr. Spalding. 



It is unquestionably a true instinct that leads a ferret to 

 thrust its long canines through the medulla oblongata of its 

 victim ; but Professor Buchanan states* that young ferrets, 

 " instead of having for their single object to put themselves 

 into a position to inflict the death wound, engage in conflict 

 with rats ;" yet they had the proper instinct, though not in 

 complete working order, for they attacked properly the 

 medulla oblongata of dead rats. Similarly I myself observed 

 with the ferrets which I reared under a hen, that when half- 

 grown and put to a rabbit for the first time, they clearly 

 knew that their attack should be directed against one end of 

 the rabbit, but were not quite certain which ; for after some 

 time of indecision they in the first instance attacked the 

 rump, and only after finding this of no use tried the proper 

 place. But of more interest still in this connection was the 

 behaviour of these ferrets when half-grown towards a fowl. 

 They had been taken away from their foster-mother, the 

 hen, some weeks previously, but still no doubt retained a 

 recollection of her. Therefore, when presented with another 

 hen, their hereditary instincts prompted attack, while their 

 individual associations inhibited the prompting. There was 

 therefore a manifest conflict of feelings, which had its ex- 

 pression in a prolonged period of indecision. And although 

 eventually the hereditary instincts prevailed over the asso- 

 ciations formed by individual experience, the prolonged 

 hesitation proved that the latter exerted a strong modifying 

 force. 



Mr. Darwin says in his MSS that in 1840 he saw some 

 chickens which had been hatched without a mother, and 



* Anns, and Mag. Nat. Hist., vol. xviii, p. 378. 



