The body of a crustacean is divided into segments, which are sometimes distinctly separated, like joints, and sometimes fused into one piece. The head part is called the /cephalic/ portion, the middle section is the /thorax/, and the posterior part is the /abdomen/. The horn-like covering of the thorax is the /carapace/; where it projects over the head it is the /rostrum/. When the head and thorax are united, as in most /Crustacea/, the anterior or front portion of the animal is called the /cephalothorax/. Each segment has a pair of appendages. Each appendage has a joint attached to the body; from this arise two jointed branches, the /endopodite/ and the /exopodite/, the inner and the outer foot. The appendages are modified to perform special functions. In front of the mouth are two pairs: the smaller ones are the /antennules/ and have ears at the base; the larger ones are /antennæ/ and are feelers. At the base of the antennæ are the /green glands/, said to have renal functions. Both the antennules and the antennæ are fringed with hairs, which aid in the sense of touch and perhaps of smell. On each side of the mouth are the /mandibles/. Then come the /maxillæ/ and the /maxillipeds/, used in capturing and tearing the food and conveying it to the mouth. Thus it will be seen that some of the appendages around the head are connected with the senses, and others are used in eating. Those of the thorax are for walking; those of the abdomen for swimming, guarding the eggs, etc. The food taken into the mouth passes into the stomach through a short passage. The stomach is divided into two parts. The front [pg247] one contains three long teeth which meet laterally and grind the food; this is known as the /gastric mill/. When sufficiently fine, the food passes through a strainer of stiff bristles into the smaller portion of the stomach, where it is partially digested, and from there enters a long, straight intestine which reaches the length of the body and opens to the outside on the under side of the /telson/, or last segment. A large liver also pours its secretions into the intestine. The green substance commonly called "fat" in lobsters is the liver. The heart consists of an elongated tube, or a short sac, which lies directly under the integument of the back. From this heart-sac, blood, which is colorless, is sent by arteries to all parts of the body; it then collects in spaces called /venous sinuses/, from which it goes to the gills, and thence back to the heart.