But they HAVE their tails in their mouths; and the reason is--" here the Mock Turtle yawned and shut his eyes.--"Tell her about the reason and all that," he said to the Gryphon.
"The reason is," said the Gryphon, "that they WOULD go with the lobsters to the dance.

So they got thrown out to sea.

So they had to fall a long way.

So they got their tails fast in their mouths.

So they couldn't get them out again.