572 



Crcatfwy of Natural . 



consists of an oval area on the top of the 

 head, traversed by numerous partitions, each 

 of which is fringed at the end by a row of 

 very numerous perpendicular teeth, or fila- 

 ments, while the whole oval space is strength- 

 ened by a longitudinal septum. 



REPTILES. (.JRcptilia.) The name given 

 to a class of cold-blooded vertebrated ani- 

 mals, whose movements are usually confined 

 to crawling and swimming, and whose res- 

 piration is aerial and incomplete. They 

 have the heart so constructed that at each 

 contraction a portion only of the blood 

 received from the various parts of the system 

 is sent into the lungs, the remainder of this 

 fluid returning into the general circulation 

 without having passed through the lungs, 

 and consequently without having been sub- 

 jected there to respiration. Hence it results 

 that the action of oxygen upon the blood is 

 less than in the Mammalia ; and though 

 several of them leap and run with celerity 

 on certain occasions, their habits are gene- 

 rally sluggish, their digestion excessively 

 slow, their sensations obtuse, and, in cold or 

 temperate climates, they pass nearly the 

 whole winter in a state of lethargy. In their 

 general form, Reptiles approach Mammalia 

 nearer than Birds ; but they oft'er in this 

 respect many variations, as may be seen by 

 comparing together, a Tortoise, a Crocodile, 

 n Serpent, and a Frog. Their head is almost 

 always small, and their body very much 

 lengthened out ; some, as Serpents, are en- 

 tirely destitute of members, or have only 

 traces of them ; but the greater number of 

 these animals, the Lizard and Frog for in- 

 stance, have four limbs, formed so as to serve 

 for walking or swimming. The skeleton in 

 this class presents much greater variations 

 in its structure, than in warm-blooded Ver- 

 tebrata. All the parts of which it is com- 

 posed are wanting in one or another group, 

 excepting the head and the vertebral co- 

 lumn ; but the bones of which these are 

 composed always preserve a great resem- 

 blance to those of Mamm alia and Birds, and 

 are easily recognized as being analagous to 

 them. Their brain, which is proportionally 

 very small, is not so essentially requisite to 

 the exercise of their animal and vital facul- 

 ties as in the Mammalia ; for they continue 

 to live and to execute voluntary movements 

 for a considerable time after being deprived 

 of the brain, and even after the loss of the 

 head : their muscles also preserve their irri- 

 tability for a considerable time after being 

 severed from the body ; and their heart con- 

 tinues to pulsate for hours after it has been 

 torn from the body. Reptiles dive with more 

 fuci li 1 v, and remain longer under water than 

 either the Mammalia or Birds, thesmallness 

 of the pulmonary vessels permitting them 

 to suspend the process of respiration, without 

 arresting the course of the blood. No Rep- 

 tile hatches its eggs. Some on quitting the 

 egg have the form and gills of fishes ; and 

 certain genera retain these organs even after 

 the development of their lungs. In other 

 Reptiles which produce eggs, the young is 

 already formed and considerably advanced 

 withiu the egg at the time the parent de- 



posits it. Reptiles also present more varied 

 forms, characters, and modes of gait, than 

 the other classes of animals ; and it is in 

 their production more especially, that Na- 

 ture seems to have tried to imagine grotesque 

 forms, and to have modified in every possible 

 way the general plan adopted for all verte- 

 brated animals, and for the oviparous classes 

 in particular. 



Reptiles are endowed with five senses, but 

 none of them in great perfection. In those 

 species which are covered with scales or 

 plates, the sense of touch is very obtuse ; 

 and in the species which have a naked skin, 

 such as the Frog, it is nlso weak, in conse- 

 quence of not being adherent to the body, 

 but envelopes it like a bag. In the Serpents 

 the eyes are immovable, destitute of eyelids, 

 and covered with a corneous substance ; in 

 some genera three eyelids are distinguish- 

 able, while others are destitute of sight. 

 Their nostrils are small, and they appear to 

 have a very weak sense of smell. They have 

 no delicacy of taste, for almost all the species 

 swallow their food entire ; and those in 

 which the tongue is soft and flexible, this 

 organ serves chiefly as an instrument for the 

 seizure of their food. None of them have 

 true fleshy lips ; and some, such as the Tor- 

 toises, are provided with a horny bill, like 

 that of a parrot; others have teeth of various 

 forms, which are not, however, formed for 

 mastication, but to assist in holding their 

 prey. Various serpents have hollow fangs, 

 which they can erect at pleasure, when they 

 open their mouths to bite, and these fangs 

 have apertures, from which they inject into 

 the wounds made by them an active and 

 deadly poison. 



From the earliest times the forms and 

 habits of the reptile world attracted at- 

 tention, and appear to have been pretty 

 well understood. The ancient monuments 

 of the Egyptians show this ; and numerous 

 passages in the Old Testament prove that a 

 similar knowledge existed when the Scrip- 

 tures were written. Nor must it be forgotten 

 that among the Organic Remains which the 

 industry and science of inquiring minds 

 have lately brought to light, none present 

 forms more wonderful, or proportions more 

 gigantic, than some of the Fossil Reptilia. 

 [See ICIITUYOSAUKUS : IOUANODOS : PLE- 



S1OSAUKUS.] 



RETEPOR A. A genus of the Polypiferous 

 corallines which is allied to Eschara, and 

 has the leaf-like expansion pierced like net- 



