Page:The New International Encyclopædia 1st ed. v. 12.djvu/404

* LIXIVIATION. 360 LIZABD. carbonates of sodium aud potassium from the ashes of wood. LIZARD (OF. lezard, lisurd, Fr. Iczard, Sp., Port. hKjarlo. It. lacerta, lizard, from Lat. lacer- tus, lanrta, lizard). A reptile of the order Lacer- tilia or Autosauria, characterized structurally by the fact that the halves of the lower jaws are connected by symphysis, that is, fused solidly together in front, while those of serpents are connected by an cUstic band ; and by the fact that the teeth are lixed. 'ilu! vcrtebrie are procii'- lous (except in most of the geckos), and have 'intercentra,' especially in the tail. The caudal vertebnp of most form's have a transverse septum of cartilage, forming a line of weakness — the point where the tail breaks off, as frequently hap- pens. The ribs of the trunk articulate by their capitula only, the reduced tuberciila Ijeing con- nected with the vertebra- by ligaments. In some groups the post-sternal ribs meet in the median abdominal line, forming bony loops ; in the Hy- ing dragons. :lie ribs support wing-like ex- pansion. Most lizards are provided with fully developed limbs and five-toed feet; but the feet are modified in the chameleons (q.v.), and in some degraded forms, as the glass-snake and especially the amphisbiena (q.v.), which burrow, the limbs have been lost not only externally but in some cases the ])elvie and pectoral girdles have completely disapjieared, accompanied by an elon- gation of the body, so that these lizards are serpent-like in form and manners. The skull is GLASS-SNAKE LIZARD. modified principally in the composition of the temporal arches; the quadrate bone is movable except in the degraded families. The hj'oid appa- ratus, extended into the tongue, is always present and well developed. In the Old World lizards the teeth are ])lanted along the top of the ridge of the jaw (acrodont), while in the New World species they are fastened to the inner side of the ridge (])leurodont) . In one American genus (Teius), the teeth of the young are pleurodont, but in the adult they become acrodont. The tongue is variously developed, but is always fur- nished with many tactile or with gustatory cor- puscles. When the tongue is very long and nar- row, it is generally forked, and in such cases, for example in the mnnitors. it is used almost en- tirely as a sensory organ. In most lizards it assists in catching the food, and in some families is an elaborate in.strunient. Salivary glands are wholly labial, and in a single genus (Helo- derma ) become poison-sacs. The digestive organs present little peculiarity, except in the cloaca, which is much modified in correlation with the strange copulatory apparatus, consisting of paired organs external to the cloaca, each a tube of erectile tissue, which can be everted like the finger of a glove. When at rest and withdrawn, the organs form slight conical longitudinal swell- ings on either side of the root of the tail. Only one organ is inserted at a time. Most lizards lay eggs, in some cases having a hard shell, but more often a parchment-like covering. The em- bryos are usually much advanced before the extrusion of the egg, and some s|)ecies, as the American horned toads, are practically vivipa- rous. The embryos within the hard-shelled eggs have an "egg-tooth' or hard point upon the end of the snout, to assist them in breaking out. Certain mysterious organs beneath the ventral skin, largely composed of fat, and hence called ■fat-bodies' (consult liutler. Proceedings of the Zuiiloyical Society of London, 18S!)), seem to be related to the sexual functions. Lizards (except degraded subterraneous forms) have good ears and eyes, the latter with movable eyelids (except in geckos) and a nictitating niend)rane; but des- ert-dwelling and other unusual forms have spe- cial adaptations elsewhere spoken of, e.g. un<ler Chameleon. Binocular vision, of course, does not occur here, any more than in other animals whose eyes look sidewise. Externally, lizards assume a great variety of shapes, from the toad-like proportions of the moloeli to the vermiform aspect of an amphis- ba'na ; but usually the head is shapely, the neck a]iiiarent. and the tail long and distinct. The tail, indeed, is of much importance in many cases as a whip-like weapon, or as .a means of safety by the ease with which it breaks oil' when seized, thereby giving the animal a chance to escape. By some species it is voluntarily thrown off in such an emergency, enabling the lizard to run to a refuge while the surprised foe is occupied with the cast-off and wriggling tail. Such lizards have the power of regenerating a tail, or rather a substitute for one. since the new tail contains in place of real vertebra; only a non-segmented rod or tube of fibro-cartilage. In most of the higher lizards the muscles, skins, and scales are reproduced, but among a variety of lower forms the scaling is abnormal, and is sometimes a reversion to an ancestral form. Consult Bou- lenger. Proceedings of the Zoijlogienl ftociety of London, 1888, page 351; and id., 1891, page 460. See Regeneration. The skin of lizards, like that of snakes, is nor- mally covered with scales, the thin, horny coat- ing of which is shed periodically: but the amphis- ba'nas have nearly lost all scales, and the glass- snake (Anguis) sheds its skin in one piece. In many eases, however, the scales are not typical, but appear as little tubercles (osteodernis), such as are seen in the geckos and Gila monster, so that the whole skin looks granular or 'pebbled'; or these dermal ossifications may be confined to the scales or shields of the head, as in the Lacer- tida". The skin is entirely devoid of glands, al- though certain minute excretory organs lie under the cutis of the thighs. Lizards vary greatly in color; the numerous desert-dwelling forms are, as a rule, of dull hue, and capable of little change, while forms dw-elling in forests or grassy places are often highly colored, and have great power of metachrosis, as is familiar in chameleons. The chromatophores, according to Gadow, are im- bedded in the deeper layers of the cutis, and send out movable contractile processes, in which their pigmental protoplasm is conveyed toward or away from the surface. Black, red, yellow and white, with their combinations of gray and brown, are the usual colors. The white pigment is made up of guanin salts. Blue and green are structural colors which are not traceable to pigment. (For the method of service of these voluntary color- changes in adaptation to surroundings, see Meta-