One morning a dead stickle-back was found in the bottom of the tank. A few days later another little fish was picked out pale and stiff.
“They are killing one another,” said Frank. “What shall we do?”
“If any more of this fighting goes on we shall have to put them back into the brook,” said Uncle George.
“Do they always fight?”
“No, not always—only in spring-time when they are mating. Look! there is one of them getting very pretty. He is the victor—the bully of the pool.”
“Let us call him Bully,” said Dolly; “he is bigger than the others, and oh, so much more beautiful.”
Next day another stickle-back was found dead, and Bully’s colours were much brighter. He darted about as if the whole tank belonged to him.
He was really a lovely fish now, and he seemed to know it by the proud way in which he dashed about, showing off his fine slender body all shiny with crimson, blue, and gold. He was, as Dolly said, “Just like a little bit of rainbow.”
But before the evening a very curious thing took place. Bully seemed to have suddenly lost all his fine colours; and instead of swimming proudly at the top of the tank, he slunk sulky to the bottom.
The strange thing was that another stickle-back—a smaller fish than Bully—was now brightly coloured, and seemed to be lord of the tank.