=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 surface when it floats or swims in a tub of water? Why? Do frogs croak in the water or on the bank? Why do they croak after a rain? Do toads croak? Are the _eggs_ laid in still or flowing water? In a clear place or among sticks and stems? Singly, or in strings or in masses? (Fig. 248.) Describe an egg. Why do frogs dig into the mud in autumn in cold climates? Why do they not dig in mud at the bottom of a pond? Why is digging unnecessary in the Gulf states? Describe the =position= of the frog when still (Fig. 250). What advantage in this position? Does the frog use its fore legs in swimming or jumping? Its hind legs? How is the frog fitted for jumping? Compare it in this respect with a jumping insect; a jumping mammal. How is it fitted for swimming? Is the general build of its body better fitted for swimming or jumping? How far can a frog jump? [Illustration: FIG. 250.--PAINTED FROG (_Chorophilus ornatus_), of Mexico.] =External Features.=--The frog may be said to have two _regions in its body_, the head and trunk. A neck hardly exists, as there is only one vertebra in front of the shoulders (Fig. 252), although most vertebrates have seven neck (cervical) vertebræ. There are no tail (caudal) vertebræ, even in the tadpole state of frogs and toads. The _head_ appears triangular in shape when viewed from what direction? The head of a frog is more pointed than the head of a toad. Is the skull a closed case of broad bones or an open structure of narrow bones? (Fig. 252.)