4 REPTILES. 



Excepting some of the tortoise tribe, tlie Reptiles are carnivorous beings, and many of 

 tliem, such as the crocodiles and alligators, are among the most terrible of rapacious creatures. 

 In this class of animals we find tlie first examples of structures which transmute Nature's 

 harmless gifts into ixjison, a cai)acity which is very common in the later orders, such as the 

 spiders and insects, and is developed to a terrible extent in some of the very lowest beings that 

 ]X)ssess animal life, rendering them most formidable even to man. 



The skeleton of a true Reptile, from which class the Bafrachians, i. e. the frogs, salaman- 

 ders, and their kin are excluded, for reasons which will presently be given, is composed of 

 well-ossified bones, and is peculiarly valuable to the physiologist. It is well known to all who 

 have studied the rudiments of anatomy, that each bone is formed from several centres, so 

 to speak, consisting of mere cartilaginous substance at its earliest formation, and becoming 

 gradually ossified from several spots. 



In the young of the higher animals these centres nre only seen during their very earliest 

 stages, and are by degrees so fused together that all trace of them is obliterated. But in the 

 Reptiles it is found that many of the bones either remain in their separate ])arts, or leave 

 so distinct a mark at the i)lace Avliere they imite, that their shape and dimensions are clearly 

 shown. In the head of the adult crocodile, for example, the frontal bone is composed of five 

 distinct pieces, the temporal of at least five pieces, and each side of the lower jaw-bone is 

 composed of either five or six portions united by sutures. 



With the exception of the tortoises, tlie Rejitiles mostly possess a goodly array of teeth, 

 set in the jaw or palate, and as a general fact, being sharp and more or less curved backward. 

 Their liodies are covered with various modifications of the structure termed the dermal, i. e. 

 skin skeleton, and are furnished with scales and plates of difl'erent forms. In some cases the 

 scales lie overlapping each other like those of the fish, in o'^liers they are modified into knobby 

 plates, and in some, of which the tortoises afi'ord well-known examples, they form large flat 

 plates on the back and breast, and scales upon the feet and legs. 



The young of Rej^tiles are produced from eggs, mostly being hatched after they liave been 

 laid, Imt in some cases the young escape fi'ora the eggs before they make their appearance in 

 the world. As a general fact, however, the eggs of Reptiles are placed in some convenient 

 spot, where they are hatched by the heat of the sun. Some species are veiy jealous about 

 their eggs, keeping a strict watch over tliem, and several of the larger serpents have a curious 

 fashion of laying the eggs in a heap, and then coiling themselves around them in a great hollow 

 cone. The size of the eggs is extremely variable, for, although as a general fact tliose of the 

 smaller Reptiles are large in proportion to the dimensions of the parent, those of the crocotliles 

 and alligators are wonderfully small, not larger than those of our domestic geese, and in many 

 cases much smaller. They are usually of a dull white color, and in some instances are without 

 a brittle shell, their covering being of a tough leathery consistence. 



In form, and often in color, the Reptiles exliibit an inexhaustible variety, and even each 

 order displays a diversity of outwai'd aspect unexampled in the two previous classes of 

 Mammals and Birds. Strange, gi-otesque, and oftentimes most repulsive in appearance, 

 though sometimes adorned with the brightest tints, the Reptiles excite an instinctive repug- 

 nance in the human breast ; and whether it be a lizard, a, snake, or a tortoise, the sudden and 

 imsuspected contact of one of these beings will cause even tlie most habituated to recoil from 

 its cold touch. This antipathy may, perhaps, liave some conue(!tion with the instinctive asso- 

 ciation of cold with death ; but whatever may be the cause, the feeling is deep and universal. 



DSP 



