You have all seen the long tail of the lobster, with its broad flaps at the end. By suddenly bending its tail underneath its body the lobster is able to propel itself backwards through the water at a great rate. The crab and the lobster are, as you may know, closely related, and the purse of the former corresponds to the tail of the latter. The purse or tail of the crab, however, is always tucked up under the body, and is never used for swimming. Both animals carry their eggs on this part of their body, and you may occasionally find a crab with its purse so full of eggs that it cannot be closed. These eggs have a curious history. When they are hatched, it is not a small crab that comes out, but a funny little creature not in the least like its parent. It has a rounded body and a long thin tail, and swims actively about. At this stage it is called a _zœa_. By-and-by the creature settles down to the sea-bottom and casts its shell. Its back is now broader and its tail shorter, and it is provided with claws; but it is still quite unlike a crab, and swims freely about. It is now known as a _megalopa_. Swarms of these may be found clustered round seaweed and other floating substances, both near the shore and in deep water. As it grows it again casts its shell, but it now tucks in its tail and settles down in life as a real crab, though of course a very small one as yet: you may find scores of them on the beach not much bigger than a split pea. Besides the green crab there are others which are common on the sea-beach. One of these is the edible crab or “partan.” This crab lives in somewhat deeper water than the other, and is of a dark reddish or purplish hue on the back, while its under parts are white. It is not nearly so quick and active in its movements as the green crab, but when it does get hold of anything it has a stronger bite. In deep water it grows to a giant size, and it is regularly caught in creels and sold for food, as its flesh is firm and good to eat. The flesh of the green crab, on the other hand, is much softer and less abundant, and it is not used for eating. Strangely enough, all crabs turn red when boiled, whatever their colour when alive. Another curious crab is sometimes found in weedy pools on the beach. This animal is of a spidery form, and is much more difficult to see than an ordinary crab, for he is elaborately disguised. His back and legs are grown over with hairy brown seaweed, and as he always lies among a mass of similar weed it is impossible to detect him so long as he remains at rest. When he does move, his movements are extremely slow. If you take him out of the water, he looks a most uncouth creature as he feebly sprawls about. Place him back in the bunch of seaweed from which he was taken, and he immediately adjusts himself so as to become invisible. This is his mode of escaping observation, for he is too slow and weak to be able to defend himself.