^H. americanus^, the common lobster of the Atlantic coast. The characteristic feature of the lobster is its enormously developed chelæ, or pincer-claws, which are on the first pair of walking-feet. Small claws occur on the next two pairs, and simple hooks on the remaining two pairs. The appendages on the abdomen are divided (biramous). In the female they are used, excepting the last pair, for holding the eggs; in the male they are greatly abridged. The appendages on the next to last segment are divided and broadly flattened, forming with the telson a powerful swimming-paddle. The rostrum is very prominent, and has a long, pointed end, slightly upturned, and several spines. The lobster belongs to the creeping forms of the order; it walks forward by means of the ten feet, but swims backward by using its caudal fin. It lives in deep water on rocky bottoms, hiding among stones, etc., but frequents sandy shores as well. It lives on dead and decaying animal matter, and it would seem strange that its flesh is so palatable, were it not that we know that chemical combinations which take place in the assimilation of food make one kind as clean, when transformed, as another. All the crustaceans have a similar dietary, being scavengers of the sea; yet fishes find them more acceptable than other animal food, and fishes capable of capturing larger prey subsist largely on the minute entomostracans described elsewhere. [Illustration: /Homarus americanus/, American lobster; male.] The lobster is so large that it can easily be dissected, and will serve as a type of the structure of /Crustacea/. In dissecting one can follow the descriptions given of the anatomy of /Crustacea/ on page 246, and will be interested in observing the beautiful arrangement of the parts and their adaptation to the uses they serve. [pg263] The female lobster carries her eggs on the abdominal legs, to which they are glued by a kind of cement. After the young emerge from the egg, the zoëæ still cling to the mother for a little time. The lobster moults eight times the first year, five times the second, and three times the third year, after which the male moults twice and the female once a year. It retires to some secluded spot for this operation, which is attended with many dangers. The back splits open longitudinally and the animal slowly withdraws, leaving the shell complete. In preparation for moulting, the lime around the contracted joints of the chelæ is absorbed, so that the soft flesh can pass through. Any injury to a limb at the time of moulting, or which results from fighting or from any accident, is repaired at successive moultings, and a lost member is replaced by a new, but not always a perfect, one. GENUS ^Panulirus^