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_