The brain of the ordinary bony fish is at a very low level. Thus the
cerebral hemispheres, destined to become more and more the seat of
intelligence, are poorly developed. In gristly fishes, like skates and
sharks, the brain is much more promising. But although the state of the
brain does not lead one to expect very much from a bony fish like trout
or eel, haddock or herring, illustrations are not wanting of what might
be called pretty pieces of behaviour. Let us select a few cases.