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1886.] Psychology. IQI 
ly, as collies are said to know sheep. The same remark applies 
generally to animals and their young. Swans, for instance, are 
said to know directly if one of their cygnets is missing, but it is 
probable that they know each young bird individually. This ex- 
planation applies with less force to the case of eggs. According to 
my bird-nesting recollections, which I have refreshed by more 
recent experience, ifa 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 rises with reference to the number of the 
victims allotted to each cell by the solitary wasps. Ammophila 
considers one large caterpillar of Noctura segetum enough; one 
species of Eumenes supplies its young with five victims; another 
ten, fifteen, and even up to twenty-four. The number appears to 
be constant in each species. How does the insect know when 
victims are still there or not. How then does she know when 
she has made up the number twenty-four? Perhaps it will be 
said that each species feels some mysterious and innate tendency 
to provide a certain number of victims. This would under no 
circumstances be any explanation, but it is not in accordance with 
the facts. In the genus (Eumenes) the males are much smaller 
than the females. Now, in the hive bees, humble-bees, wasps, and 
other insects, where such a difference occurs, but where the young 
are directly fed, it is of course obvious that the quantity can be 
proportioned to the appetite of the grub. But in insects with the 
habits of Eumenes and Ammophila the case is different, because 
the food is stored up once for all. Now, itis evident that if a 
female grub was supplied with only food enough for a male, she - 
would starve to death; while ifa male grub were given enough 
for a female it would have too much. No such waste, however, 
occurs. In some mysterious manner the mother knows whether 
the eggs will produce a male or female grub, and apportions the 
quantity of food accordingly. She does not change the species 
or size of her prey; but if the egg is male she supplies five, if 
female ten, victims. Does she count? Certainly this seems very 
like a commencement of arithmetic. At the same time it would 
could count; and whether, for instance, it could realize some very 
simple sum, such as that two and two make four. But when we 
