The Story is from the Sutra of Parables, told by the Buddha in a sermon:
Once upon a time, there was a turtle living in a pond. Because of the very dry weather, the pond was drying up and the turtle got out of the pond to ask for help. He saw two ducks passing by and shouted out, "Help! Would you please bring me to a pond full of water?"
"How can we help you out?" asked the ducks. "We are flying in the air and you are swimming in water."
"I propose that both of you carry each ends of a piece of stick with you by your mouths, " replied the turtle. "Then I hold on to it at the middle with my mouth. You can then carry me to a pond full of water."
"That is a good idea," said the two ducks. "We will help you out. But you must remember not to open your month."
So, the duck carried the turtle across the country side toward the lake. As they passed over a village, a group of children looked at them and bursted into laughter, "Look! What a funny sight! Two ducks carrying a stick with a turtle holding onto it with his month!"
The turtle was angry at the remark and reply, "you guys are stupid. What do you understand?" But, once he opened his month, he fell from sky and crashed to death.