Instructional series: The Frog. The frog is an AMPHIBIAN (aquatic, also breathes air) intermediate vertebrates between reptiles and fish. Look at this frog (skin, mouth, nostrils, throat). The skin is naked and humid. In spring, the Frog lays a great number of eggs that make a floating mass. The number of eggs equals that of the black spots. Some eggs looked at closely (pressed one against the other, they no longer are spehrical). Here is an egg under a loupe: the center (Vitellus) is black; the white is transparent; there is no shell limestone. A frog egg a week after the hatching - what do you notice? The little black ball (Vitellus) changed its appearance - it is an embryo now. Day 13 - a marvelous transformation took palce - the embryo began to move. This little creature moves in the center of the egg, what does he have on each side of his head? Gills it uses to breath in water. He turns about himself, as if suspended; notice his fat head, his heavy body, and the thinned tail. Day 25: the embryo leaves the egg. He strives to separate from the egg. He became a tadpole, and eats aquatic plants. His gills are no longer visible but internal. He swims, waving his tail laterally. Observe this tadpole. Did you notice at birth the little paws the tail has? The back legs develop first. The front ones develop next and the tail is reabsorbed; METAMORPHOSES of the Tadpole. How many different forms do you see? Frolics of our five young subjects. The frog leaves the water, breathes air freely, it has lungs. It breathes, with a closed mouth: observe its nostrils, and neck, it swallows air by deglutition. Its front paws are more slender and shorter than the back paws. Front paw, how many figers does it have? Rear paw, how many fingers does it have, what do you notice? Thanks to its long and strong posterior paws, the Frog jumps…. …and swims, note the locations of its fingers and membranes. What is this large and sticky mass that is oulled out of the Frog's mouth? It's the tongue, attached to the edge of the jaw, it can completely exit the mouth. Almost invisible, the Frog watches its prey. In projecting its tongue it glues and ceases the larvae and insects the it gets rid of for us. END