he
blue vault overhead, he added earnestly--"Ah, my boy, remember they have
a wiser teacher than you or I! However, you're wrong about their being
all similar. The majority of those you've caught are certainly of the
ordinary species of green crab and uneatable, if even they had been of
any tolerable size; but, that little fellow there is a young `velvet
fiddler' or `swimming crab.' If you notice, his hind legs are
flattened, so as to serve him for oars, with which he can propel himself
at a very good rate through the water if you give him a chance. Look
now!"

"I see," cried Bob eagerly. "He's quite different to this other chap
here with the long legs."

"Oh that is a `spider crab.' He is of very similar proclivities to his
cousin though he lives ashore. The cunning fellow uses his sprawling
long limbs in lieu of a web, and will lie in wait in some hole between
the rocks, artfully poking his claws out to catch unwary animals--often
those of his own or kindred species--as they pass by his den."

"What is this queer little chap?" asked Nellie, pointing to another,
which was partly concealed in an old whelk-shell. "He seems to want to
get out and can't."

"Why, my dear, that is the `hermit crab.' He does not want, though, to
leave that comfortable lodging he has secured for himself, as you think.
He's an `old soldier,' and knows when he's well off! He belongs to
what is called the `soft-tailed' family, and being defenceless astern he
has to seek an artificial protection against his enemies, in place of
natural armour."

"How funny!" said Nellie, watching the little animal more closely.
"What a queer fellow!"

"Yes," continued the Captain, "and, that is the reason why he goes
prowling about for empty shells. Often, too, really he's such a
pugnacious fellow, he will turn the rightful tenant out, taking forcible
possession. Just look at his tail and see how it is provided with a
pair of pincers at the end. He is enabled by this means to hold on
firmly to any shell, no matter how badly it may fit him, which he
chooses for his temporary habitation."

As he spoke, the Captain extracted with some little difficulty the
buccaneer crab from the whelk-shell, showing its peculiar formation,
quite unlike that of the others. A young shrimp who had lost his
latitude was also found in Bob's pond, and the discovery led the old
sailor to speak of these animals that form such a pleasant relish to
bread-and-butter; an