28G KErxILIA. 



These animals have neither scales nor carapace, but the body is invested ^vith a naked faiid 

 moist] skin, [over the surface of which the blood receives much of its oxygenation.] Witli 

 the exception of one genus, they have no nails to the toes. 



The envelope of their egp:;s is simply membranous, and in most cases these arc fecundated 

 as thev issur forth, the mah' attui/hinjj,' Inmsulf to the other sex ni order to he snnultancous. 



Their ep:L!:s or spawn enl;irge very much in the water after tliev have been hud. The young 

 not onh" ditfcrs from the adult liy the ])resence of its gdls, Ijut its feet are oidv developed hy 

 degrees, and m several genera there are also a deciduous beak and tail, and intestines of a 

 different form. Some of the species are even viviparous. 



Tiiii Frogs {Rana, Lin.) — 

 Have four legs and no tail in their aduU state. Their head is flat, the muzzle rounded, the mouth 

 deeply cleft, and the greater number have a soft tougue attached only to the lower part of the gullet, 

 but which extends forward to the jaw, and is doubled back above. Their fore-feet have only four 

 toes, but the hinder sometimes show the rudiment of a sixth. 



Their skeleton is entirely deprived of ribs. A cartilaginous plate, even with the head, takes the 

 place of tympanum, and renders the ear visible externally. The eye has two llesliy lids, and a third, 

 which is lioriziintal ami ii"ans[iarent, eonei-'aleil l)y the lower one. 



Tlic inspiration of air is produced siiitjily by the movements of the muscles of tlic throat, which, b\ 

 dilating, draw in the air through the nostrils, and, liy contraeling, wliilst the oritices of the iiobtrils 

 are cloi^ed by means of the tongue, force the air into the lungs. Expiration, on the eonirary, is 

 elfected by the contmction of the muscles of the lower belly : so that, by tipening the beUy of the 

 hving animal, the lungs will distend without any power ot" contraction, arid l.iy holding opeu the 

 mouth the animal will become asphyxiated, for want of air sent into the lungs. 



The embraces of the male are excessively prolonged : in reference to which the thumb of this sex 

 is furnished with a spongy swelling, which enlarges during the season, and which is designed to aid 

 in grasping. The eggs are fecmidated at the moment they are laid, and the young is termed a ladpole. 

 It is at first provided with along fleshy tail, and a small horny beak, hut with no other apparent 

 members besides certain littU' fringes at the sides of the neck. Tliese disappear afti_-r ^ome days, but 

 Swammcrdam assures us that they still exist as %\\\% underneath the skin. The lattcrare minute 

 crests, which are very numerous, attached to the four cartilaginous arches placed on each side of the 

 neck adhering to the hyoid hone, and en\eloped by a meudironous tunic, which is covered by the 

 genei'al skin. Tlie wati^r, entering by the mouih, to bathe the intervals of these cai'tilaginous arclu'S, 

 passes out either hy twt) orifices or by a single one, according to tlie species, piurced through the 

 external skin, either on the niiddle or on the left side of the animal. The hind feet are gradually 

 developed to view, by bttle and little, while the anterior likewise appear beneath the skin, Imt do not 

 burst it for some time later. The tail is absorbed hy degrees. The beak fails, and oceasions the 

 genuine mandibles to appear, wdiieh had jireNioiisly Iteen soft, and were concealed underneath the skin. 

 The gills shriid; and are obliterated, leaving the huigs to perform tlieir fLmctions unassisted by them. 

 The eye, whieh in tlie Tadpole was only visible tluongb a thinner space in the skin, liecLunes 

 apparent with its three lids. The intestines, previtm^ly \er\ long, slender, and s-pirally contorted, 

 shorten, and acquire the enlargement of stomach and colon : the Tadpole living solely upon ai[uatic 

 vegetation, \\liiUt the adult animal preys on insects and oilier animal substances. Fuially, the limbs 

 of the Tadpi.ile reprtjihice the parts of them (hat had been mntilateil, nearly as in the Newts. 



The particular epoch of each of these several charges varies, according to the species. 



In temperate and cold climates, the perfect animal buries itself, during winter, under grouml, or in 

 the mud below the surface of water, where it continues to live without food or respiration, [lievoud 

 what of the latter is effected by the surface of the skin] ; although, during the warm season, if it l.ic held 

 for a few minutes only with the mouth Ojicn, so as to impede the ]u-ocess of respiration, it iicrishes. 



Thk Frogs, properly so called, {Rana, Laurenti), — 

 Have a slender body, and the hind limbs \ery long, ami more or Icsn palniatcd ; their skin is smooth 

 and slippery ; their n[)per jaw snpphed all rouml with a range of minutely line teeih, and they have an 



