Exercises on Lesson VIII.
1. What is an aquarium? 2. Why are water weeds and water snails put into an aquarium? 3. How do you feed small fish? Why should you be careful not to put in more than the fishes can eat? 4. Where does the stickle-back lay its eggs?
IX.—TADPOLES.
The frog spawn, when first put into the big glass bell, was just a mass of jelly-like stuff studded all over with black dots.
When looked at closely, it was seen to consist of many round, clear eggs. Each egg was surrounded by a thin skin, and had, in its centre, a little round black ball or yolk.
At the end of a week all these black yolks had lost their round shape. They were now long and oval. During the next four days these oval yolks became little moving animals, each having a head, body, and tail, but no limbs.
From the head of each there grew out two pairs of feathery objects. These, Uncle George told the boys, were gills or breathing organs. Soon another pair of these feathery gills appeared: so that each little creature had now three on each side of his head.
By the end of the second week the little creatures had all wriggled out of the eggs. They hung together by their feathery gills in little black groups.
“What shall we feed them on?” Frank asked his uncle.
“They are not at all nice in their tastes,” Uncle George replied. “They will eat almost anything, from water weeds up to drowned kittens. If they get nothing else, they will eat one another, and not mind it a bit.”