318 DR. G. J. ROMANES ON THE MENTAL [June 4, 
of fruit as payment. In this way the ape was eventually taught to 
associate these three numbers with their names. Lastly, if two 
straws or three straws were demanded, she was taught to hold one 
straw or two straws in her mouth until she had picked up the 
remaining straw, and then to hand the two straws or the three straws 
together. ‘This prevented any possible error arising from her 
interpretation of vocal tones—an error which might well have arisen 
if each straw had been asked for separately. 
As soon as the animal understood what was required, and had 
learnt to associate these three numbers with their names, she never 
failed to give the number of straws asked for. Her education was 
then extended in a similar manner from three to four, and from 
four to five straws. Here, for reasons to be presently stated, I allowed 
her education to terminate. But more recently one of the keepers 
has endeavoured to advance her instruction as faras ten. The result, 
however, is what might have been anticipated. Although she very 
rarely makes any mistake in handing out one, two, three, four, or five 
straws, according to the number asked for, and although she is 
usually accurate in handing out as many as six or seven, when the 
numbers eight, nine, or ten are named, the result becomes more and 
more uncertain, so as to be suggestive of guesswork. It is evident, 
however, that she understands the words seven, eight, nine, and ten 
to betoken numbers higher than those below them; and if she is 
asked for any of these numbers (i. e., above six), she always gives some 
number that is above six and not more than ten; but there is no 
such constant accuracy displayed in handing out the exact number 
named as is the case below six. On the whole, then, while there is 
no doubt that this animal can accurately compute any number of 
straws up to five, beyond five the accuracy of her computation 
becomes progressively diminished. 
It is to be noticed that the ape exhibits some idea of multiplica- 
tion ; for she very frequently (especially when dealing with numbers 
above five) doubles over a long straw so as to make it present two 
ends, and thus to appear as two straws. Any of the comparatively 
rare errors which she now makes in dealing with numbers below 
six are almost invariably due to her thus endeavouring to duplicate 
her straws. In this connexion it is to be remembered that, owing 
to the method above described (whereby the ape is required to place 
each straw separately in her mouth until the sum asked for is com- 
pleted), when any high number is demanded, a considerable tax is 
imposed upon her patience; and as her movements are deliberate 
while her store of patience is but small, it is evident to all observers 
that the doubling of the straws is intended to save trouble by getting 
the sum completed with greater rapidity than is possible when every 
straw is picked up separately. Of course we do not recognize these 
doubled straws as equivalent to two straws, and therefore the persis- 
tency with which she endeavours to palm them off as such is the 
more noteworthy as evidence of her idea of multiplication. More- 
over, I am disposed to think that the uncertainty which attends her 
dealing with the numbers six and seven is more largely due to her 
