258 COMPARATIVE ZOOLOGY 



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 

 booklets 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 pro- 

 longed, 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 lar- 

 val 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 for- 

 mer group, the oral apparatus consists of two pairs of 



