Are the =eyes= on the top or on the sides of the head, or on both? Can a fish shut its eyes? Why, or why not? Is the eyeball bare, or covered by a membrane? Is the covering of the eyeball continuous with the skin of the head? Is there a fold or wrinkle in this membrane or the surrounding skin? Has the eye a pupil? An iris? Is the eye of the fish immovable, slightly movable, or freely movable? Can it look with both eyes at the same object? Is the _range of vision_ more upward or downward? To the front or the side? In what direction is vision impossible? Can a fish close its eyes in sleep? Does the eyeball appear spherical or flattened in front? The ball is really spherical, the lens is very convex, and fish are nearsighted. Far sight would be useless in a dense medium like water. In what direction from the eyes are the =nostrils= (Fig. 211.) There are two pair of nostrils, but there is only one pair of nasal cavities, with two nostrils opening into each. There are no nasal passages to the mouth, as the test with a probe shows that the cavities do not open into the mouth. What two functions has the nose in man? What function has it in the fish? [Illustration: FIG. 210.—BLACKBOARD OUTLINE OF FISH. ] There are _no external_ =ears=. The ear sacs are embedded in the bones of the skull. Is hearing acute or dull? When you are fishing, is it more necessary not to talk or to step lightly, so as not to jar the boat or bank? [Illustration: FIG. 211.—HEAD OF CARP. ] What is the use of the large openings found at the back of the head on each side? (Fig. 211.) Under the skin at the sides of the head are thin membrane bones formed from the skin; they aid the skin in protection. Just under these membrane bones are the gill covers, of true bone. Which consists of more parts, the membranous layer, or the true bony layer in the gill cover? (Figs. 211 and 212.) Is the =mouth= large or small? Are the _teeth_ blunt or pointed? Near the outer edge, or far in the mouth? (Fig. 212.) Does the fish have lips? Are the teeth in one continuous row in either jaw? In the upper jaw there are also teeth on the premaxillary bones. These bones are in front of the maxillary bones, which are without teeth. Teeth are also found in the roof of the mouth, and the tongue bears horny appendages similar to teeth. Are the teeth of the fish better suited for chewing or for grasping? Why are teeth on the tongue useful? Watch a fish eating: does it chew its food? Can a fish taste? Test by placing bits of brown paper and food in a vessel or jar containing a live fish. Is the throat, or gullet, of the fish large or small? [Illustration: FIG. 212.—SKELETON OF PERCH. ]