all this you see that the mouth of the lobster is well armed with teeth and scissors to tear and cut its food. Counting from the front, it has first the true jaws (mandibles); then the two pair of little jaws (maxillæ); and these are followed by the three pair of foot-jaws (maxilli

pedes) making, altogether, six pair, which are all turned up against the mouth. In front of the jaw are two very long jointed feelers called antennæ, but you seldom see them at their full length (Fig. 15); they are easily broken (Fig. 19). Next to the feelers (antennæ) are two

Eye.

Eye stalk.

FIG. 21.

little feelers, or antennules (Figs. 15, 20); and last of all, in front, comes a pair of joints which support the eyes (Fig. 21), called the optic pair of appendages. Now let us begin with the eyes, and go back to the tail, to see how many pairs of feelers, jaws, hands, feet,

and paddles the lobster owns (Fig. 15). He has six pairs attached to the head, eight pair to the breast (thorax), and six pairs to the body (abdomen); in all, twenty pairs, and very few of these appendages are alike.

You now have a pretty good idea of the exo-skeleton, or hard outside part of the lobster, and we shall look next at the soft parts inside (Fig. 22). The mouth seems a very good place to begin at, and you will find it between the mandibles, or jaws. In front of it is a lip, shaped like an escutcheon, and is called the labrum, which means lip. At the back of the mouth is another lip, the metastoma, meaning beyond the mouth, and this is looked upon as the lower lip. The mouth, as in the mussel, opens into a gullet, or œsophagus. This meat-pipe opens into a four-cornered box (Fig. 22)-the stomach-which is very curiously made.

Near the centre of the box the walls come almost together, dividing it into two parts: the front part is the larger, and it is called the cardiac end, because in the human body the first part of the stomach points toward the heart, but you see, in the lobster, it points away from the heart. It contains three strong, colored teeth, fastened to a T-shaped frame (Fig. 23), and worked by muscles which are fastened to the inside of the breastplate (carapace). These teeth meet in the middle of the stomach, and form a powerful grinding-machine, which crushes the food like the stones in a mill (Fig. 24). Sometimes, when you find the empty shell of a lobster on the sea-shore, you can see a perfect mould of the old mill-" the mill-wheel gone to decay." How the lobster gets out of his shell, and how he turns the mill out of his stomach, we shall study after a while. The small back part of the

stomach is called the pyloric end, and it is made inside like a sieve or strainer. The sides are stuffed out in the centre like cushions, and quite covered with hairs (Fig. 25). Let us see why. Pylorus means gate-keeper. It protects or guards the intestine from all intruders,

such as big pieces of meat and hard bodies. None but the finest particles can pass through the strainer, and hence this pylorus is a very good gate-keeper. The intestine does not go wandering about in the body like the mussel's, but passes straight back (Fig. 22), and ends at the

anus, at the under part of the tail-piece (telson). On each side of the cephalo-thorax lies a long, soft, yellowish-green mass. This is the liver, and it opens into the small, pyloric end of the stomach by several ducts or pipes on each side. Away up in the front part of the cephalo-thorax, at the base of the feelers (antennæ) on either side

Tooth.

Tooth.-

T-shaped Frame.

Tooth.

FIG. 28. THE LOBSTER's MILL.

you may see a soft green mass called the "green gland" (Fig. 22). This is supposed to be the kidney. Next we will take a look into the side-chambers (Fig. 22) of the cephalo-thorax, and see what the three pair of walking-legs, the great pincers (chelæ), and the two pairs of jaw-feet, are doing in there. In each chamber we find eighteen little,

tapering, feathery-like bodies. Each has a central stem, surrounded by fine, feathery filaments. They look very much like so many little bottle-brushes (Fig. 22). These are the gill-plumes, and this room is called the gill, or branchial chamber. The gills are placed in two sets, six in one and twelve in the other. The first row is fastened to

the six feet or appendages of the breast (thorax) which we found pushing themselves up into the chamber (Fig. 22). The other twelve are fastened to the pleuron or side-pieces of the cephalo-thorax. These gills are not covered with stiff hairs (cilia) as the mussel's, so there must be some other plan of moving the water. There is a very curious piece of machinery at the front entrance. You remember the oval or boat-shaped plate in front of the chamber, formed by the hindmost little jaw (maxilla). This plate is called the scapho-gnathite, which means the little skiff-like jaw. It is made on the plan of the Archimedean screw, and it works as the screw of a propeller, and is set in motion by the jaws. The water enters the back part of the gillchamber by a slit, and it is scooped out by the screw through the opening in front, bubbling and frothing as it goes. Thus the mechanism of the screw was all worked out in our little lobster long years before it was discovered by the great Archimedes. The tiny net-work of the blood-vessels is spread over the framework of the gill-plumes, just as you found it on the lattice-work of the mussel's gill-pockets. As the screw propels the water through the branchial or gill chamber the blood takes out the oxygen from the air in the water, and gives back carbonic acid. You remember how the strong hairs (cilia) of the pockets sweep the water along over the mussel's gills, and how the little blood-vessels take up their oxygen and give up their carbonic acid. The gills that are fastened to the legs move when the legs move, and the faster they go the more water they use. So much for the lobster's breathing or respiration. We will leave his circulation, his muscles and nerves, for another chapter.

The eyes, as you have seen, are away in front (Figs. 15, 22) at the ends of the first pair of appendages-the eye-stalks. The eye is kidney-shaped; instead of having one window or pupil as your eye has, through which the light enters, the whole front is divided into squares like old-fashioned window-panes (Fig. 26). Each square is really a separate eye, and this is what is called a compound eye. The lob