254 GEOKGE JOHN EOMANES 



of a very accurate observer, and as he adds that they 

 are ' always to be repeated when the attempt is 

 made,' so that they are regarded by him as ' among 

 the very commonest instances of animal sagacity,' 

 we cannot lightly set them aside. The observer in 

 question is Leroy, and the facts for which he 

 personally vouches in his work on animal intelligence 

 are briefly as follows : 



< The rooks will not return to their nests during 

 daylight should they see that anyone is waiting to 

 shoot them. If to lull suspicion a hut is made below 

 the rookery and a man conceal himself therein, he 

 will have to wait in vain, should the birds have ever 

 been shot at from the hut on a previous occasion. 

 Leroy then goes on to say : ' To deceive this suspicious 

 bird, the plan was hit upon of sending two men into 

 the watch-house, one of whom passed out while the 

 other remained ; but the rook counted and kept her 

 distance. The next day three went, and again she 

 perceived that only two returned. In fine, it was 

 found necessary to send five or six men to the watch- 

 house in order to throw out her calculation.' 



Finding it on this testimony not incredible that a 

 bird could count as far as five, I thought it worth 

 while to try what might be done with a more 

 intelligent animal in this connection. Accordingly, 

 about a year ago, I began, with the assistance of the 

 keeper, to instruct the chimpanzee at the Zoological 

 Gardens in the art of computation. The method 

 adopted was to ask her for one, two, three, four, or 

 five straws, which she was to pick up and hand out 

 from among the litter in her cage. Of course, no 



