In what state of growth are the legs when the tadpole first goes to the surface to breathe? Which legs appear first? What advantage is this? What becomes of the tail? Is the tail entirely gone before the frog first leaves the water? Are tadpoles habitually in motion or at rest?
Is the intestine visible through the skin? (Fig. 249.) Is it straight or coiled? Remembering why some fish have larger intestines than others, and that a cow has a long intestine and a cat a short one, state why a tadpole has a relatively longer intestine than a frog.
Compare the mouth, jaws, eyes, skin, body, and habits of tadpole and frog.
Frogs
Prove that frogs and toads are beneficial to man. Did you ever know of a frog or toad destroying anything useful, or harming any one, or causing warts? How many pupils in class ever had warts? Had they handled frogs before the warts came? Frogs are interesting, gentle, timid animals. Why are they repulsive to some people?
Environment.—Where are frogs found in greatest numbers? What occurs when danger threatens them? What enemies do they have? What color, or tint, is most prominent on a frog? Does the color "mimic" or imitate its surroundings? What is the color of the under side of the body? (Fig. 250.) Why is there greater safety in that color? What enemies would see water frogs from below? Do tree frogs mimic the bark? The leaves?
Can a frog stay under water for an indefinite time? Why, or why not? What part of a frog is above the
