What is to be said of the behaviour of beavers who gnaw the base of a tree with their chisel-edged teeth till only a narrow core is left--to snap in the first gale, bringing the useful branches down to the ground? What is to be said of the harvest-mouse constructing its nest, or of the squirrel making cache after cache of nuts? These and many similar pieces of behaviour are fundamentally instinctive, due to inborn predispositions of nerve-cells and muscle-cells. But in mammals they seem to be often attended by a certain amount of intelligent attention, saving the creature from the tyranny of routine so marked in the ways of ants and bees. Sheer Dexterity Besides instinctive aptitudes, which are exhibited in almost equal perfection by all the members of the same species, there are acquired dexterities which depend on individual opportunities. They are also marked by being outside and beyond ordinary routine--not that any rigorous boundary line can be drawn. We read that at Mathura on the Jumna doles of food are provided by the piety of pilgrims for the sacred river-tortoises, which are so crowded when there is food going that their smooth carapaces form a more or less continuous raft across the river. On that unsteady slippery bridge the Langur monkeys (_Semnopithecus entellus_) venture out and in spite of vicious snaps secure a share of the booty. This picture of the monkeys securing a footing on the moving mass of turtle-backs is almost a diagram of sheer dexterity. It illustrates the spirit of adventure, the will to experiment, which is, we believe, the main motive-force in new departures in behaviour. [Illustration: _Photo: Lafayette_ ALSATIAN WOLF-DOG An animal of acute senses and great intelligence. It was of great service in the war. (The dog shown, Arno von Indetal, is a trained police dog and did service abroad during the war.)] [Illustration: _Photo: W. S. Berridge._ THE POLAR BEAR OF THE FAR NORTH An animal of extraordinary strength, able with a stroke of its paw to lift a big seal right out of the water and send it crashing along the ice. The food consists chiefly of seals. The sexes wander separately. A hole is often dug as a winter retreat, but there is no hibernation. A polar bear in captivity has been seen making a current with its paw in the water of its pool in order to secure floating buns without trouble--an instance of sheer intelligence.] [Illustration: _From the Smithsonian Report_, 1914 AN ALLIGATOR "YAWNING" IN EXPECTATION OF FOOD Note the large number of sharp conical teeth fixed in sockets along the jaws.] Power of Association A bull-terrier called Jasper, studied by Prof. J. B. Watson, showed great power of associating certain words with certain actions. From a position invisible to the dog the owner would give certain commands, such as "Go into the next room and bring me a paper lying on the floor." Jasper did this at once, and a score of similar things.