Mr Nugent explained how they have to look out for an unoccupied shell, or perhaps eat up the occupant, and then wriggle in their own tails.
The hermit crab grows bigger, but the shell does not, so, when he feels his tail pinched, he has to look out for a larger home. It is amusing to watch him crawling along, examining shell after shell, till he has discovered one to his satisfaction. Then, when he has ascertained that it is unoccupied, he whisks his tail out of one and as rapidly pops it into the new one.
Mr Nugent pointed out that one claw was much larger than the other, and he showed how, when the hermit wishes to withdraw itself into its shell, he can perfectly coil himself away by doubling up the little claw and closing the larger one over it.
Digby was really much interested in the number of star-fish, and shells, and sea-weeds, and many other things, about which his uncle did not think it wise to enter on long explanations to him.
With the next haul of the trawl they were not nearly so successful, giving them an idea of the precarious nature of the fisherman’s calling; while in the third there was scarcely a fish, but Mr Nugent pronounced it more prolific than any of the former ones to him.
It was now time to return home. The net was thoroughly washed, and then triced up in the rigging, while the beam was lashed alongside.
Julian had begun to recover, but he was very unlike himself, and not at all inclined to talk and boast; indeed, Power remarked that he had never seen him so agreeable since he had come to Osberton.
Digby had been examining the crustacea with grave attention, the lobsters, crabs, and shrimps, when, lifting up one, he exclaimed, “It’s very odd; I always thought they were red. How is it, uncle, that these are black?”
A loud laugh from his companions was their reply to the question.
“You are thinking of the lobsters you have seen brought to the table cooked, and ready to be eaten,” observed Mr Nugent. “But go on, Digby, never be ashamed of asking questions, although, now and then, they may bring down a laugh upon you. It would fare but ill with the poor crabs and lobsters if they were not black, or rather of the colour of the rocks and weeds among which they live. Their colour thus enables them to escape detection from the sharp-sighted fish, which are constantly swimming rapidly about in search of them, and, in spite of their coats-of-mail, easily gobble them up. But I was going to show you this little pea-crab, Pinnotheres. He is said to have established a friendship with the inhabitant of a bivalve shell, the Pinna, or Sea-wing. When he wants to go out in search of food, the Pinna opens her shell, and lets him out. He, argus-eyed, watches the approach of their mutual enemy, the Polypus, and instantly rushes back, and by his return giving notice of danger, the shell closes, and both are safe. Otherwise the Polypus might get one of his rays inside the Pinna, and destroy its vitality in a moment, or he might touch the crab, and kill it in the same way. When the pea-crab discovers a supply of food he brings it to his friend, the Pinna, to be divided equally. I will not vouch for the truth of this account; and I am afraid that Master Pinnotheres has some more interested motive in his attachment, and may, in the end, eat up his friend, the Pinna, out of house and home.”