Merla and the earth people watched the busy little creatures for some time before they were themselves observed, but finally Trot gave a laugh when one crab fell on its back and began frantically waving its legs to get right-side-up again.  At the sound of her laughter they all stopped their play and came toward the visitors in a flock, looking up at them with their bright eyes in a most comical way.

“Welcome home!” cried one as he turned a back somersault and knocked another crab over.

“What’s the difference between a mermaid and a tadpole?” asked another in a loud voice, and without a pause continued, “Why, one drops its tail and the other holds onto it.  Ha, ha!  Ho, ho!  Hee, hee!”

“These,” said Merla, “are the clown crabs.  They are very silly things, as you may already have discovered, but for a short time they are rather amusing.  One tires of them very soon.”

“They’re funny,” said Trot, laughing again.  “It’s almost as good as a circus.  I don’t think they would make me tired, but then I’m not a mermaid.”

The clown crabs had now formed a row in front of them.  “Mr. Johnsing,” asked one, “why is a mermaid like an automobile?”

“I don’t know, Tommy Blimken,” answered a big crab in the middle of the row.  “Why do you think a mermaid is like an automobile?”

“Because they both get tired,” said Tommy Blimken.  Then all the crabs laughed, and Tommy seemed to laugh louder than the rest.

“How do the crabs in the sea know anything ’bout automobiles?” asked Trot.

“Why, Tommy Blimken and Harry Hustle were both captured once by humans and put in an aquarium,” answered the mermaid.  “But one day they climbed out and escaped, finally making their way back to the sea and home again.  So they are quite traveled, you see, and great favorites among the crabs.  While they were on land they saw a great many curious things, and so I suppose they saw automobiles.”

“We did, we did!” cried Harry Hustle, an awkward crab with one big claw and one little one.  “And we saw earth people with legs, awfully funny they were; and animals called horses, with legs; and other creatures with legs; and the people cover themselves with the queerest things—­they even wear feathers and flowers on their heads, and—­”

“Oh, we know all about that,” said Trot.  “We live on the earth ourselves.”

“Well, you’re lucky to get off from it and into the good water,” said the Crab.  “I nearly died on the earth; it was so stupid, dry and airy.  But the circus was great.  They held the performance right in front of the aquarium where we lived, and Tommy and I learned all the tricks of the tumblers.  Hi!  Come on, fellows, and show the earth people what you can do!”

At this the crabs began performing their antics again, but they did the same things over and over, so Cap’n Bill and Trot soon tired, as Merla said they would, and decided they had seen enough of the crab circus.  So they proceeded to swim farther up the rocky canyon, and near its upper end they came to a lot of conch shells lying upon the sandy bottom.  A funny-looking crab was sticking his head out from each of these shells.