  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.” “How dreadful,” said Frank. “Hadn’t we better give them something to eat now, for fear they may eat each other up.” “It wouldn’t do much good giving them anything to eat now, for they have no mouths.” The Development of the Tadpole. “No mouths, Uncle George?” “No mouths,” Uncle George repeated. “Is it not curious? For four days the tadpole, or young frog, has no mouth, and yet during that time he grows a great deal. “Four days after he leaves the egg his mouth Just as Uncle George had said, the tadpoles ate nothing for four days. Then their mouths appeared, and they began to eat the water weeds. But Uncle George fed them on raw meat. He said it made them grow quickly. A small piece of raw beef, tied to the end of a string, was lowered into the tank, and the tadpoles swarmed around it. What was left of the beef was pulled out every morning, and a fresh piece put in. By this means the water was kept clean, and had only to be changed once a week. “Why, they have no gills now,” said Frank one day, as he was helping his uncle to change the water. “Oh yes, they have, Frank. They have gills like a fish now. “When they are about four weeks old, their feathery gills go away; but, before this, four gill-slits are formed in each side of the tadpole’s head.” Uncle George took a glass tube about twelve inches long, and placing his thumb tightly on one end of it, he pushed it down into the water until the other end was right above a tadpole. Then he took his thumb off, and the tadpole and some water shot up the tube. He then replaced his thumb tightly on the end of the tube, and lifted it out of the water. The tadpole and water remained in the tube as long as he kept his thumb on the end of it. He emptied “I can’t see the gill-slits,” said Frank. “Oh yes, you can, if you look closely. What seems to be a big head is really head and body covered over by a cloak of skin.” “Yes, I see the gills now,” said Frank. “They are red in colour. I also see the cloak. There is an opening on the left side of it.” “That is so,” said his uncle. “That opening is there to let the water into the gills.” At the end of the fifth week, Uncle George took some tadpoles out for the boys to look at. “Do you see any change?” he asked. “Yes,” said Tom, “they have two things like hind legs growing out.” “These are legs,” his uncle said, “and in two weeks from now these legs will have movable joints in them.” Day by day the tadpoles were carefully watched, and the following wonderful changes were observed. When about seven weeks old, their hind legs became jointed, and long toes were formed. The tadpoles were now able to kick out and swim by means of their long hind legs. Their gills went away, and they came to the surface and took mouthfuls of air. They now had lungs instead of gills. But the most striking change came at the end of the eleventh week. One by one they lost the cloak which covered head and body. Under this cloak a pair of fore legs had been folded The clumsy tails grew smaller and smaller daily. At last there was no tail left, and what was at one time a cluster of black, wriggling tadpoles, was now a crowd of lively little dark yellow frogs. The boys wished to keep them longer, but their uncle told them that they could not do this. “Your tadpoles are now frogs,” he said. “The frog is an insect eater. As we cannot give these little frogs their natural food, we must place them where they can get it for themselves, or they will die.” So the frogs were carried back to their native pond. Exercises on Lesson IX.
Frog, Toad, and Newt—showing Eggs of Toad and Newt, and Tadpoles of Frog and Toad |
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