Tadpole and Fish Fable of Comprehension

Michael Dickmann: Here's what the story is. There was this little tadpole and a fish that grew up in a pond, and they were always intensely curious about life outside the pond. And then, eventually, the tadpole grows into a frog and discovers that, because he's an amphibian, he can go out and see what life is like. So he comes back and tells the fish what he's seen. He says, "Well, look, one of the things is that there's neat creatures called birds that can actually fly in the air, and they ...

 An Experiment With a Tadpole's Development

An early classic experiment by the Nobel Prize-winning embryologist Roger Sperry illustrates the principle perfectly. Sperry and a colleague took a tadpole and removed a tiny square of skin from the back. They removed another square, the same size, from the belly. They then regrafted the two squares, but each in the other's place: the belly skin was grafted on the back, and the back skin on the belly. When the tadpole grew up into a frog, the result was rather pretty, as experiments in embryo...