counted and kept her distance. The next day three went, and again she
perceived that only two retired. In fine, it was found necessary to send
five or six men to the watch house to put her out in her calculation. The
crow, thinking that this number of men had passed by, lost no time in
returning.' From this he inferred that crows could count up to four.
Lichtenberg mentions a nightingale which was said to count up to three.
Every day he gave it three mealworms, one at a time. When it had finished
one it returned for another, but after the third it knew that the feast was
over.... There is an amusing and suggestive remark in Mr. Galton's
interesting _Narrative of an Explorer in Tropical South Africa_. After
describing the Demara's weakness in calculations, he says: 'Once while I
watched a Demara floundering hopelessly in a calculation on one side of me,
I observed, "Dinah," my spaniel, equally embarrassed on the other; she was
overlooking half a dozen of her new-born puppies, which had been removed
two or three times from her, and her anxiety was excessive, as she tried to
find out if they were all present, or if any were still missing. She kept
puzzling and running her eyes over them backwards and forwards, but could
not satisfy herself. She evidently had a vague notion of counting, but the
figure was too large for her brain. Taking the two as they stood, dog and
Demara, the comparison reflected no great honour on the man....' According
to my bird-nesting recollections, which I have refreshed by more recent
experience, if a nest contains four eggs, one may safely be taken; but if
two are removed, the bird generally deserts. Here, then, it would seem as
if we had some reason for supposing that there is sufficient intelligence
to distinguish three from four. An interesting consideration arises with
reference to the number of the victims allotted to each cell by the
solitary wasps. One species of Ammophila considers one large caterpillar of
_Noctua segetum_ enough; one species of Eumenes supplies its young with
five victims; another 10, 15, and even up to 24. The number appears to be
constant in each species. How does the insect know when her task is