! LOBSTER (ante). A mere inspection will show that a lobster is composed of two principal parts. These are commonly called the head and the tail. That which is called the head is really the head and the thorax combined, and is technically called the ceplialothoritx; while the part called the tail is the abdomen. Like all annulosa (artic ulata), the lobster is composed of a number of annular segments, or parts representing such, with members—legs, jaws, claws, feelers, ete.—attached to them, the whole being inclosed iu a chituous shell. See Cimix, ante. These segments may be separated one by one, with the members attached to them, and examined. Each segment is composed of a convex upper plate called the terguin, and closed beneath by a flatter plate called the sternum, while the side of the segment is called the pleuron. These segments are again subdivided into parts which are amalgamated, but it is sufficient for the purposes of this article to give only a general description. There are 21 segments in the whole body, 7 in the head, 7 in the thorax, and 7 in the abdomen. The ceplialothorax, or the part called the head, is covered with a shield or carapace, sometimes called the cephalic buckler, composed of an enormous development of tergal or dorsal pieces. The first segment of the head is provided with long, movable eye-stalks or peduncles, bearing upon their ends the compound eyes. 'The next six segments of the head, from before backwards, are furnished with: first, the antennules or smaller antennte, each composed of a basilar piece called a protopodite, and two somewhat elongated feelers or antennai; next, the larger antennw, each composed of a protopodite, and a single, greatly elon gated feeler; next, the biting jaws or mandibles. between which is the aperture of the mouth, bounded behind by a forked process called the labium, and in front by a broad plate called the labrurn dr upper lip. The next two segments after this are provided with appendages called, respectively, the first and second pairs of maxillte, each situ ated upon a protopodite, with terminal joints, which in the first pair are rudimentary, but in the second are provided with spoon-shaped joints, called scaphognathites, whose office is to cause a current of water to pass through the gill-chamber by constantly bailing water out of it. The next and last segment of the head (according to IIuxley this belongs to the thorax) bears one of the three pairs of modified limbs, called maxillipedes, or foot-jaws. These are legs with the ordinary structure of a protopodite, and three other joints added, called exopodite, endopodite, and epipodite. These limbs are modified so as to aid the purposes of mastication. This description applies to the next two pairs of segments, and which belong to the thorax, according to the usual division. The third
pair of appendages of the thorax (the fourth according to Huxley) are the great claws, or chelm. The next two pairs of thoracic limbs are also provided with nippers or chelte, but they are much smaller. The last two pairs are similar, except that they are termi nated by simple, pointed joints, and not chelm. These last two pairs, however, differ, in that the next last pair has attached to its protopodite a process which serves to keep the gills apart. Of the segments of the abdomen, seven in number, five—all except the first and last—are provided with appendages called swimmerets. Each swimmeret consists of a basal joint and two diverging joints. The basal joint is the protopodite, the outer of the diverging joints the exopodite, and the inner one the endopodite. In next to the last segment (the last one which has appendages), the swimmerets are greatly expanded, so as to form powerful paddles. The last segment of the abdomen is called the telson; it has no appendages, and for this reason soine authorities do not regard it as a segment, but as an azygos appendage, or, in other words, an appendage without a fellow. The first segment of the abdomen will be seen to be considerably modified from those bear ing swimmerets.—An esophagus leads from the mouth into a globular-shaped stomach, containing a calcareous apparatus for grinding food. This kind of mill is called the lady in the lobster. The intestine passes without convolutions in a nearly straight course to the anal aperture, which is situated on the under-side just in ,front of the telson. The lobster has a well developed liver, consisting of two lobes, which enter the intestine by separate ducts. The heart is a muscular sack situated in the back just beneath the cara. pace, and opens by valvular apertures into a surrounding venous sinus, called (improp erly) the pericardium. The gills are pyramidal, lance-shaped bodies, situated imme diately beneath the heart and attached to the bases of the legs. Each consists of a central stem supporting numerous land/1m, and they are unprovided with cilia. Water is propelled through them by the movetnents of the legs and by the spoon-shaped joint of the second pair of maxillaz above-mentioned, which is constantly in motion, bailing out water in front of the branchial chamber, thus allowing the entrance of fresh water through the posterior aperture. The nervous system is situated along the ventral sur face of the body, and consists of a series of ganglia united by commissural cords. Two compound eyes, two pairs of antennte or feelers, and two ears in the form of sacks com prise the special org,ans of sense. The arrangement of the muscular system is in general like that of all articulates.