Mrs. Frog would not at first let her son go, but promised that as soon as the tadpole lost his tail, and his flippers had turned into fore legs, and his hind quarters had properly sprouted, so that he could hop out of danger, he might then venture on his travels.
"Dutch Fairy Tales for Young Folks"
William Elliot Griffis
The wings, in which form the fore-limbs are specialized, represent the same elements as our own hands; and other modifications of the same members have produced the paws of cats and dogs, the hoofs of horses and cattle, and the flippers of whales and porpoises,-to mention no others.
"The Old Riddle and the Newest Answer"
John Gerard
Not only did they rise and splash and roll and indolently flick themselves with their great flippers, but they stood upright on their tails, like Alice's carpenter's companion, and one fondled its young as a water-mamma should.
"Edge of the Jungle"
William Beebe