“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 the contents of the tube into a little dish, and Frank looked at the tadpole with a glass.
“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.