never one limb alone. The clawed animals, like the cat and lion, make use of their feet in securing prey, all four limbs being furnished with curved retractile claws; but the food is conveyed into the mouth by the movement of the head and jaws. Man and the monkeys employ the hand in bringing food to the mouth, and the lips and tongue in taking it into the cavity. The thumb on the human hand is longer and more perfect than that of the apes and monkeys; but the foot of the latter is also prehensile.

2. The Mouths of Animals. In the parasites, as the tapeworm, which absorb nourishment through the skin, and insects, as the May fly and botfly, which do all their eating in the larval state, the mouth is either wanting or rudimentary. The amoeba, also, has no mouth proper, its food passing through the firmer outside part of the bit of protoplasm which constitutes its body. Mouth and anus are thus extemporized, the opening closing as soon as the food or excrement has passed through.

In the infusoria the "mouth" is a round or oval opening leading through the cuticle and outer layer of protoplasm to the interior of the single cell which makes their body. It is usually bordered with cilia, and situated on the side or at one end of the animal (Figs. 9, 11).

An elliptical or quadrangular orifice, surrounded with tentacles, and leading directly to the stomach, is the ordinary mouth of the polyps and jellyfishes. In those which are fixed, as the actinia, coral, and hydra, the mouth looks upward or downward, according to the position in which the animal is attached (Figs. 17, 34, 236); in those which freely move about, as the jellyfish, it is generally underneath, the position of the animal being reversed (Fig. 22). In some, the margin, or lip, is protruded like a proboscis; and in all it is exceedingly dilatable.

The mouth of the starfish and sea urchin is a simple round aperture, followed by a very short throat. In the starfish, it is inclosed by a ring of hard spines and a membrane. In the sea urchin it is surrounded by a muscular membrane and minute tentacles, and is armed with five sharp teeth, set in as many jaws, resembling little conical wedges (Fig. 226).

Among the headless mollusks, the oral apparatus is very simple, being inferior to that of some of the radiate animals. In the oyster and bivalves generally, the mouth is an unarmed slit a mere inlet to the esophagus, situated in a kind of hood formed by the union of the gills at their origin, and between two pairs of delicate flaps, or palpi. These palpi make a furrow, along which pass the particles of food drawn in by the cilia, borne by cells which cover the surface of the flaps.

Of the higher mollusks, the little clio (one of the pteropods) has a triangular mouth, with two jaws armed with sharp horny teeth, and a tongue covered with spiny hooklets all directed backward. Some univalves have a

simple fleshy tube or siphon. Others, as the whelk, have an extensible proboscis, which unfolds itself, like the

finger of a glove, and carries FIG. 218.-Jaw of the Common Snail within it a rasplike tongue, (Helix albolabris) greatly magnified.

which can bore into the hardest shells. Such as feed on vegetable matter, as the snail, have no proboscis, but on the roof of the mouth a curved horny plate fitted to cut leaves, etc., which are pressed against it by the lips, and on the floor of the mouth a small tongue covered with delicate teeth. As fast as the tongue is worn off by use, it grows out from the root.

The mouth of the cuttlefish is the most elevated type below that of the fishes. A broad circular lip nearly

DODGE'S GEN. ZOÖL. — 17

conceals a pair of strong horny mandibles, not unlike the beak of a parrot, but reversed, the upper mandible being the shorter of the two, and the jaws, which are cartilaginous, are imbedded in a mass of muscles, and move vertically. Between them is a fleshy tongue

covered with teeth.

The parasitic worms, living within or on the outside. of other animals, generally have a sucker at one end or underneath, serving simply for attachment, and another which is perforated. The latter is a true suctorial mouth, being the sole inlet of food. It is often surrounded with hooklets or teeth, which serve both to scarify the victim and secure a firm hold. In the leech, the mouth is a triangular opening with thick lips, the upper one prolonged, and with three jaws. In many worms it is a fleshy tube, which can be drawn in or extended, like the eye stalks of the snail, and contains a dental apparatus inside (Fig. 215).

Millepedes and centipedes have two lateral jaws and a four-lobed lip.

In lobsters and crabs the mouth is situated underneath the head, and consists of a soft upper lip, then a pair of upper jaws provided with a short feeler, below which is a thin bifid lower lip; then follow two pairs of membranous under jaws, which are lobed and hairy; and next, three pairs of foot jaws (Fig. 54). The horseshoe crab has no special jaws, the thighs answering the purpose. The barnacle has a prominent mouth, with three pairs of rudimentary jaws.

With few exceptions, the mouths of insects in the larval state are fitted only for biting, the two jaws being horny shears. But in the winged, or perfect, state, insects may be divided into the masticating (as the beetle) and the suctorial (as the butterfly). In the former group, the oral apparatus consists of two pairs of

horny jaws (mandibles and maxilla), which work horizontally between an upper (labrum) and an under (labium) lip. The maxillæ and under lip carry sensitive jointed feelers (palpi). The front edge of the labium is

3

FIG. 219.Mouth of a Locust, dissected and much magnified: 1, labrum, or upper lip; 2, mandibles; 3, jaws; 4, labium, or lower lip; 5, tongue. The appendages to the maxillæ and lower lip are palpi.

commonly known as the tongue (ligula).75 In such a mouth, the mandibles are the most important parts; but in passing to the suctorial insects, we find that the mandibles are secondary to the maxillæ and labium, which are the only means of taking food. In the bee

tribe, we have a transition between the biting and the sucking insects—the mandibles "supply the place of trowels, spades, pickaxes, saws, scissors, and knives," while the maxillæ are developed into a sheath to inclose the long, slender, hairy tongue which laps up the sweets of flowers. In the suctorial butterfly, the lips, mandibles, and palpi are reduced to rudiments, while the

maxillæ are excessively lengthened into a proboscis, their edges locking by means

FIG. 220.- Head of a Wild Bee (Anthophora retusa), magnified, front view : a, compound eyes; b, clypeus; c, three simple eyes; d, antennæ; e, labrum; f, mandibles; i, maxillæ; h, maxillary palpi; 7, palpifer; j, labial palpi; m, paraglossæ; k, ligula.

of minute teeth, so as to form a central canal, through which the liquid food is pumped up into the mouth. Seen under

the microscope, the proboscis is made up of innumerable rings interlaced with spiral muscular fibers. The proboscis of the fly is a modified lower lip; that of the bugs and mosquitoes, fitted both for piercing and suction, is formed by the union of four bristles, which are the mandibles and maxillæ strangely altered, and encased in the labium when not in use.