LOGIC OF RECEPTS. 57 



rookery and a man conceal himself in it with a gun, he waits 

 in vain if the bird has ever before been shot at in a similar 

 manner. " She knows that fire will issue from the cave into 

 which she saw a man enter." 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 on while 

 the other remained ; but the crow counted and kept her dis- 

 tance. 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 put her out 

 of her calculation." 



Now, as Leroy is not a random writer, and as his life's 

 work was that of Ranger at Versailles, we must not lightly 

 set aside this statement as incredible, more especially as he 

 adds that the " phenomenon is always to be repeated when 

 the attempt is made," and so is to be regarded as "among 

 the very commonest instances of the sagacity of animals."* 

 If it is once granted that a bird has sagacity enough 

 to infer that where she has observed two men pass in and 

 only one come out, therefore the second man remains behind, 

 it is only a matter of degree how far the differential perception 

 may extend. Of course it would be absurd to suppose that 

 the bird counts out the men by any process of notation, but 

 we know that for simple ideas of number no symbolism in the 

 way of figures is necessary. If we were to see three men pass 

 into a building and only two come out, we should not require 

 to calculate 3 — 2=1 ; the contrast between the simultaneous 

 sense-perception of A -f B -f C, when receptually compared 

 with the subsequently serial perceptions of A and B, would 

 be sufficient for the spontaneous inference that C must still be 

 in the building. And this process would in our own case 

 continue possible up to the point at which the simultaneous 

 perception was not composed of too many parts to be after- 

 wards receptually analysed into its constituents.! 



* li'id., pp. 125, 126. 



t Professor Prcyer has ascertained experimentally llic number of objects (such 

 as shot-corns, pins, or dots on a piece of paper), which atlmit of being siinul- 



