Considered in this sense it is interesting to observe to what extent the intelligence even of a fish reaches--and I think upon reflection it will be found that the fish is as clever as any creature could be in its position. I deny altogether that the cold-blooded fish--looked on with contempt so far as its intellectual powers are concerned--is stupid, or slow to learn. On the contrary, fish are remarkably quick, not only under natural conditions, but quick at accommodating themselves to altered circumstances which they could not foresee, and the knowledge how to meet which could not have been inherited. The basking jack is not alarmed at the cart-horse's hoofs, but remains quiet, let them come down with ever so heavy a thud. He has observed that these vibrations never cause him any injury. He hears them at all periods of the day and night, often with long intervals of silence and with every possible variation. Never once has the sound been followed by injury or by anything to disturb his peace. So the rooks have observed that passing trains are harmless, and will perch on the telegraph wires or poles over the steam of the roaring locomotive. Observation has given them confidence. Thunder of wheels and immense weight in motion, the open furnace and glaring light, the faces at the long tier of windows--all these terrors do not ruffle a feather. A little boy with a wooden clapper can set a flock in retreat immediately. Now the rooks could not have acquired this confidence in the course of innumerable generations; it is not hereditary; it is purely what we understand by intelligence. Why are the rooks afraid of the little boy with the clapper? Because they have noticed his hostile intent. Why is the basking jack off the instant he hears the light step of a man?