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.”[47] 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+B+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 afterwards receptually analysed into its constituents.[48] In this connection also I may state that, with the assistance of the keeper, I have succeeded in teaching the Chimpanzee now at the Zoological Gardens to count correctly as far as five. The method adopted is to ask her for one straw, two straws, three straws, four straws, or five straws—of course without observing any order in the succession of such requests. If more than one straw is asked for, the ape has been taught to hold the others in her mouth until the sum is completed, so that she may deliver all the straws simultaneously. For instance, if she is asked for four straws, she successively picks up three straws and puts them in her mouth: then she picks up the fourth, and hands over all the four together. This method prevents any possible error arising from her interpretation of vocal tones, which might well arise if each straw were asked for separately. Thus there can be no doubt that the animal is able to distinguish receptually between the numbers 1, 2, 3, 4, 5, and understands the name for each. Further than this I have not attempted to take her. I may add that her performance has been witnessed by the officers of the Zoological Society and also by other naturalists, who will be satisfied with the accuracy of the above account. But the ape is capricious, and, unless she happens to be in a favourable mood at the time, visitors must not be disappointed if they fail to be entertained by an exhibition of her learning.