Boulenger[[115]] has figured and further described the eggs and young. The egg measures 6-10 mm. in diameter, and is a transparent capsule in which the young frog is coiled up in the same way as figured by Peters in Hylodes martinicensis; but none of the specimens, which are in an advanced stage of development, show anything of a tail. There are no gills, but on each side of the abdomen are several regular transverse folds, the function of which is probably that of breathing organs, like the tail of Hylodes. The tip of the snout is furnished with a small conical protuberance projecting slightly through the delicate envelope of the egg, and evidently used to perforate that envelope.
R. guppyi, likewise an inhabitant of the Solomon Islands, is a giant among frogs. It was discovered by Mr. Guppy on the Shortland Islands. The type-specimen measures 165 mm. = 6½ inches in length! The skin of the upper parts is covered with minute warts, and forms a strong fold above the distinct, but small, tympanum. General colour dark olive brown above, dirty white below.
R. tigrina is a common species of Eastern Asia, including the Malay Islands. On account of the strength of its voice, and its size, which is said to reach 7 inches, it is called the "Indian Bullfrog." Mainly aquatic, it has a strong cutaneous fringe along the outer side of the fifth toe. The skin of the back is thrown into longitudinal folds, and a strong fold marks the upper border of the tympanum. The general colour above is olive brown, with dark spots, often with a light vertebral line; the under parts are white. The male has a pair of large external vocal sacs.
R. gracilis has the same distribution, but it remains much smaller, and the toes are only half, instead of fully, webbed.
R. catesbiana is now the settled name of the "Bullfrog" of North America, the much more appropriate name of mugiens having been sacrificed to the fetish of priority. The tympanum is extraordinarily large, at least equal to the size of the eye, largest in the male. The first finger does not extend beyond the second; the toes are connected by a broad web down to the ends, and there is a small inner, but no outer, metatarsal tubercle. The upper parts are olive brown, clouded with dark brown or blackish spots; the under parts are yellowish white, often marbled with brown, especially on the throat. The iris is reddish, with an outer yellow ring. The male possesses two internal vocal sacs. Total length of adult specimens about 5 inches, but there are giants on record 7 inches in length, while the stretched hind-limbs measure another 9 or 10 inches. Its home extends over the whole of the United States, East of the Rocky Mountains, southwards into Mexico, northwards into Canada.
According to Holbrook the Bullfrogs are solitary in their habits, only collecting together in the breeding season, when hundreds may be seen in the same small pond; and then the croak uttered by the males is so loud as to resemble the distant roaring of a bull, and can be heard on still evenings at a distance of half a mile. The voice is a hoarse bass "brwoom," playfully translated into "more rum." "They cannot be said to abound, but are found commonly enough sitting half immersed in water, or on the banks of ponds, waiting for their prey. If alarmed they hop suddenly into the water, but do not conceal themselves at once, frequently skimming along the surface for several yards before they dive below." They are the most aquatic of all the North American frogs, and Holbrook has known specimens to live in wells for years, where they could not rest a moment on solid ground above the water.
The Bullfrog is voracious, and takes almost anything that lives or gets into his own pond–Mollusca, Crustacea, fishes and, above all, frogs. There is no doubt that they drag down and swallow a good many ducklings and the young of other water-fowl, but certainly not the half-grown birds which have a way of disappearing from the farms wherever there are negroes and other farm-hands about. In turn the bullfrog has sufficient enemies to keep its numbers down, in fishes, birds, otters, and snakes, and, in the South, alligators. Although easily kept and growing comparatively tame, they are dull, having to be kept in solitary confinement on account of their greediness, which knows no limits. Two of our specimens each swallowed a full-grown Salamandra maculosa, and died within the same night, probably not understanding the meaning of the conspicuous black and yellow warning colours of the European.
E. clamata s. fontinalis, likewise an inhabitant of Eastern North America, may be called a smaller edition of the Bullfrog, its usual full-grown size being about 3½ inches. The tympanum is conspicuously large, but the toes are webbed to a lesser extent, and the skin forms a glandular fold which extends from the shoulder in a curve to the flank. This species is partial to the neighbourhood of running streams; it is said to be exceedingly timid, and to utter a short cry when disturbed and making its enormous leaps.
Another North American relation is R. halecina s. palustris, frequenting the neighbourhood of ponds and rivers, very lively and capable of jumping 8 to 10 feet. The tympanum is smaller than the eye, but there is the same glandular lateral fold as in R. clamata. The vocal sacs are internal and decidedly small.
