186 
COMPARATIVE ZOOLOGY. 
they select with wonderful sagacity; and Monkeys avoid 
poisonous berries; Bees and Squirrels store up food for 
the future; Bees, Wasps, and Spiders construct with mar¬ 
vellous precision ; and the subterranean chambers of Ants 
and the dikes of the Beaver show engineering skill; while 
Salmon go from the ocean up the rivers to spawn; and 
Birds of the temperate zones migrate with great regu¬ 
larity. 
But in the midst of this automatism there are the glim¬ 
merings of intelligence and free-will. We see some evi¬ 
dence of choice and of designed adaptation. Pure in¬ 
stinct should be infallible. Yet we notice mistakes that 
remind us of mental aberrations. Bees are not so eco¬ 
nomical as has been generally supposed. A mathemati¬ 
cian can make five cells with less wax than the Bee uses 
for four; while the Humble-bee uses three times as much 
material as the Hive bee. An exact hexagonal cell does 
not exist in nature. Flies lay eggs on the carrion-plant 
because it happens to have the odor of putrid meat. The 
domesticated Beaver will build a dam across its apartment. 
Birds frequently make mistakes in the construction and 
location of their nests. In fact, the process of cheating 
animals relies on the imperfection of instinct. Nor are 
the actions of the brute creation always perfectly uni¬ 
form ; and, so far as animals conform to circumstances, 
they act from intelligence, not instinct. There is proof 
that some animals profit by experience. Birds do learn 
to make their nests; and the older ones build the best. 
Trappers know well that young animals are more easily 
caught than old ones. Birds brought up from the egg, 
in cages, do not make the characteristic nests of their 
species; nor do they have the same song peculiar to their 
species, if they have not heard it. Chimney-swallows cer¬ 
tainly built their nests differently in America three hun¬ 
dred years ago. A Bee can make cells of another shape, 
