The phenomena of cutaneous absorption, exhalation, and respiration have derived their fullest illustration and explanation from experiments made on the soft and naked skin of the frog. Thus this despised creature has rendered the greatest services to anatomy, physiology, physics, and chemistry, and has thrown light which no other animal could on the functions of innervation, muscular contractility, circulation, respiration, absorption, and generation. The frog is not only a graceful and harmless animal, but is actually useful in destroying insects and slugs injurious to vegetation. Though in England and the United States frogs are rarely eaten by man, in France and southern Europe they are largely consumed as food; they are caught in various ways, and are preserved in large "froggeries" until wanted for the table; the flesh is most delicate and nutritious at the time when they are about to enter their winter quarters, yet great numbers are eaten in the spring, when they are more easily caught; the hind limbs are generally the only part eaten, and these are cooked in various modes, in all of which they are as much more delicate than chicken as that is superior to veal and pork.

In the materia medica the flesh of frogs has long been used by continental physicians as the basis for anti-scorbutic and restorative broths.-The largest species of the genus rana in the United States is the bullfrog (7?. pipiens, Latr.), which often measures when extended 18 or 21 in.; the general color above is green in front, dusky olive behind, with irregular black blotches, and below yellowish white, with dusky marks; the limbs dusky, with black bars. The bullfrog, so called from its loud voice, is rather solitary in its habits, living about stagnant and sluggish water, not very abundant in one place except during the breeding season; it is the most aquatic of the frogs, and an excellent swimmer, often living for years in wells, where it is allowed to remain under the supposition that it purifies the water; it is also an active leaper, taking to the water when alarmed. Its voracity is extreme; it devours young ducks, snakes, moles, mice, insects, worms, snails, its own tadpoles, and any small animal it can catch; it does not seize prey unless alive or in motion.

The species is very generally distributed over the United States. The spring frog (R. fontinalis, Le Conte) is green above, with dusky spots behind; throat and abdomen yellow; hind limbs dark green, with dusky bars; a cutaneous fold or ridge from the orbit to the hind legs; the total length is about 8 1/2 in.; it is fond of springs of cold water, and feeds on worms and insects; it is common from Maine to Virginia. The marsh frog (R. palustris, Le Conte) is pale brown above, with two longitudinal rows of dark brown square spots on the back and sides, yellowish white below, with the posterior half of the thighs bright yellow mottled with black; it is slender and delicately formed, about 8 in. in total length; it is found from Maine to Virginia, on the borders of marshes and pools, and sometimes at a great distance from water; it has a peculiar strong and disagreeable odor; from its being a favorite bait for pike, it is often called the pickerel frog. The shad frog (R. halecina, Kalm) is one of the handsomest species, being green above, with ovate spots of dark brown margined with yellow, and yellowish white beneath; it is about 8 1/2 in. in total length, active, and able to leap a distance of 8 to 10 ft. when alarmed; it is called shad frog from its appearing in the middle states in the spring with this fish; it is also called water and leopard frog; it is very widely distributed in the United States, and is the nearest representative here of the common frog of Europe, being like that sought after by epicures.

The wood frog (R. sylvatica, Le Conte) is pale reddish brown above, and yellowish white below; the head has a dark brown stripe extending from the snout to the tympanum through the eye; the total length is a little over 5 1/2 in.; it is found from Michigan to the Carolinas, chiefly in thick woods, preferring those of oak; it is active, when pursued hiding itself under leaves; it rarely approaches water except in the breeding season. The crying frog (E. clamitans, Bosc), a slender species, is olive-colored in front, dusky behind, and silvery white below; the total length is 8 1/2 in.; it is very active, and when leaping frightened into the water utters a short loud cry; it is a southern species, taking the place of the spring frog of the north, and by some thought to be the same.-Like all other reptiles, the common frog of Europe (R. temporaria, Linn.) differs from all American species; the color is generally brown, inclining to reddish or yellowish above, with irregular spots of black or brown, and transverse bands on the legs, and yellowish white below with smaller and fewer spots; the most constant mark is an elongated brown patch behind the eye on each side; the total length is about 7 in.; it is found very generally over Europe. The green frog of Europe (R. esculenta, Linn.) is of a general greenish color above, with black or brownish marks, and sometimes with three yellow stripes on the back, and yellowish white below; the total length is about 8 in.; it is distributed over Europe, Asia, and northern Africa, and is the species most sought after for food.-There are several species of small frogs, principally American and subtropical, belonging to the genus cystignathus (Wagler), characterized by the almost entire absence of webs to the toes; for their description the reader is referred to the work of Dr. Holbrook (vol. i.), and of Dumeril and Bibron (vol. viii.). The genus ceratophrys (Boie) or phrynoceros (Tschu-di) will be described under Horned Frog; the tree frogs (hyla, Lanrenti) and the peeping frogs {hylodes, Fitz.) will be noticed under Tree Frog, belonging as they do to the family hy-ladoe.-The frogs are considered by Agassiz lower than the toads among anourous batra-chians, on account of their aquatic habits, the persistence of the embryonic webs between the toes, and the non-existence of glands developed in the substance of the skin.

The family ra-nidoe are the most numerously represented of the fossil anourous batrachians, and their remains occur in the tertiary and diluvian formations, sometimes of large size. The gigantic chcirotherium or labyrinthodon is placed by Jager, Fitzinger, and Owen among batrachians; this immense frog-like animal, with a head 2 or 3 ft. long and the body 10 or 12, first appeared in the carboniferous period, was abundant in the triassic, and probably disappeared before the Jurassic epoch. From the facts now ascertained it would appear that the muddy shores and flats of remote geological ages were inhabited by batrachoid forms as strange as the flying pterodactyl or the great ichthyosaurus and plesiosaurus, and that possibly frogs 12 ft. long (like cheirotherium) leaped and croaked in the ancient marshes.

Eight stages of development of the tadpole, from the recently hatched (1) to the adult form (8), as illustrated by St. George Mivart.

1. Bullfrog (liana pipiens).

2. Northern Bullfrog (Rana Horiconensis).

1. Shad Frog (Rana halecinal.

2. Marsh Frog (Rana palustris).

1. Wood Frog (Rana sylvatica).

2. Spring Frog (Rana fontinalis).

Common Frog (Rana temporaria).

Green Frog (Rana esculenta).