"While you think, no doubt, that you could teach them better, eh?" said the Captain chuckling; but, the next moment, raising his hat and a graver expression stealing over his face as he looked upward towards the 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; and he told them that one of the best fishing-grounds for them was off the Woolsner Shoal, some four miles further along the beach to the eastwards, while another good place was Selsea Bill, more eastward still.