I have been observing for several days the movements of a Common Shore-Crab, which has been almost all his life under my protection. Although his present dimensions would render such a feat impossible, when first I shook the little fellow off a bunch of _C. officinalis_, he could have crawled with the greatest of ease into the mouth of a small popgun. We all know that members of this family are bold and daring in their attacks upon their weaker neighbours; upon each and all they wage a constant predatory warfare. The poor Pholades, however, are the favourite objects of their attacks. On these innocent bivalves the Crustacea successfully prey, unless they are protected by their usual rock-bound citadel, which, of course, they cannot always be. In order to watch the Pholas at work, it is necessary that the siphons should be more or less protruding from his tubular dwelling. If supported, say, to the full depth of his valves, the animal is secure; for I notice that neither crab nor fish can tear away the gristly ends of the siphonal appendages when withdrawn; and when disturbed, the poor Pholas leaves only this part in view. I have frequently seen the Fiddler-Crab embrace a Pholas in his claws, and struggle to pull him from his seat. On one occasion this operation was performed successfully, much to my annoyance, as I had been at some trouble to saw the rock away in order to watch easily every movement of the animal within. At night when I looked into the tank my pet was safe; next morning it was wedged under some pebbles, and the crab was feasting leisurely upon his tender flesh. It is most amusing to watch the Blennies, too, attack a Pholas, cast into the tank, and to witness their mode of pecking at and shaking their victim, and turning innumerable somersaults with it in their mouths. The strength they exhibit in these manœuvres is perfectly astounding. About two hours after they had received one of their favourite 'muttons' to feast upon, I peeped into the aquarium, and found, as I expected, the Blennies hard at their work of destruction. Behind them, among some bushy tufts of _I. edulis_, the little crab, before alluded to, was seated. In his arms he held an object unlike anything I had seen on sea or land. It appeared like a slender stick of beautifully iridescent opal. My amazement at this sight may readily be conceived, for I had not the remotest idea as to how he had become possessed of such a prize. Next day I placed another devoted Pholas in the tank, and after a while looked in to see how its finny enemies were conducting themselves, when, what should meet my eye, but the crab, sneaking off with another opal baton in his arms! I was more puzzled than ever. It was quite certain that the object in question had been procured from the Pholas, yet I had not heard of, or ever seen anything like it in that animal.