Chapter XI: Part I: Amphibia (10)

This pretty creature inhabits most of the warm portions of the continental Indian region, from India and Ceylon to South China and Malacca. The back is a rich dark brown, divided from the yellow of the head by a narrow black line which extends from eye to eye and forwards to each nostril. A conspicuous yellow band runs from the eyes to the hind-limbs. The sides of the body and the limbs are mottled yellow and brown. The under parts are dirty buff; the throat of the male is black. The intensity of colouring varies individually and from time to time, the contrast between the brown and yellow being occasionally very brilliant. Total length up to 3 inches, the male being the smaller sex.

"I have been told by both English and natives that this frog was unknown in Singapore until some nine or ten years ago, when it was introduced by a half-caste (why, it is not known), and that it rapidly spread about the island. It is now well known as the 'Bullfrog' by the English in Singapore, and detested for the noise it makes at night. The voice of these rotund animals can be heard every night after heavy rain; it is {235}a deep guttural croak, 'wau-auhhhh,' very strident and prolonged. The males croak while floating on the surface of the water, the single vocal sac under the mouth inflated like a globe, and the arms and legs extended. They can hop well on land and are good swimmers. The skin is excessively slimy; the secretion comes off profusely, and dries on the hand into a sort of white gum, with a faint aromatic smell. This gum dissolves in hot water and coagulates in cold. The general appearance of these frogs is very stout, their girth being about twice the length from snout to vent. The tongue, which is oblong in spirit specimens, in life is very elastic, assuming, when extended, a vermiform shape and reaching about 4 cm. in length. They appear after sunset, crawling on old wood and feeding on white ants."

SUB-FAM. 2. DYSCOPHINAE.–_With teeth in the upper jaw._

This small group of nine genera, with scarcely more than one dozen species, all with one exception living in Madagascar, has been separated by Boulenger from the Engystomatinae merely on account of the presence of teeth on the upper jaw and on the vomerine margin of the palatine bones. He himself remarks that _Calluella_ may be considered a toothed _Hypopachus_, and _Plethodontohyla_ a toothed _Callula_. These are obvious cases of convergent analogy. Except for the teeth, the Indian _Calluella_ would be merged into the American _Hypopachus_, and this would present an instance of the most puzzling geographical distribution. In the case of the other two genera, one Indian and Malayan, the other Malagasy, no such suspicion would arise, since there are many other instances of such a coincidence of distribution. There is the same divergence or unsettled condition in the modification of various parts in the Dyscophinae as in the Engystomatinae. The precoracoid bars are weak and curved backwards, and closely pressed against the strong coracoids, in _Dyscophus_, _Calluella_ and _Platypelis_, while these elements are reduced to unossified bars, and the clavicular portions completely lost, in _Plethodontohyla_ and in _Phrynocara_. The omosternum is absent and the metasternum is small in all except _Dyscophus_, in which both these parts are exceptionally well developed and large, although remaining unossified. The palate of _Dyscophus_ and _Calluella_ is provided with curious, serrated dermal folds like those which are so common in the Engystomatinae; and well-developed discs on the fingers and toes, supported by T-shaped phalanges, are {236}possessed by _Platypelis_, _Cophyla_ and others. The sacral diapophyses are dilated. The pupil is either horizontal or vertical. Those which are provided with discs to the fingers and toes are climbers, and mostly slender and long-legged, sometimes of very small size, for instance _Cophyla_, the body of which is scarcely one inch in length.

The genera can be determined by means of the following key:–[103]

_A_. Pupil vertical. Palatine teeth in long transverse series.

_a_. Precoracoids ossified. Tips of fingers and toes not dilated.

Sternum very large. Madagascar .......... _Dyscophus._

Sternum small. Burmah .......... _Calluella._

_b_. Precoracoids not ossified. Tips dilated ..........
_Plethodontohyla._

_B_. Pupil horizontal.

_a_. Palatine teeth in long transverse series.

α. Precoracoids ossified. Tips dilated.

Fingers and toes free. Precoracoids entirely ossified ..........
_Mantipus._

Fingers and toes webbed at the base. Precoracoids semi-ossified
.......... _Platyhyla._

β. Precoracoids not ossified. Tips not dilated ..........
_Phrynocara._

_b_. Palatine teeth in one or two small groups.

Precoracoids ossified. Tips dilated.

Two small groups of palatine teeth .......... _Platypelis._

One single group in the middle of the palate .......... _Cophyla._

No teeth on the palate .......... _Anodontohyla._

_Dyscophus antongili._–Madagascar. General appearance stout, with short legs and a wide mouth. Total length about 3 inches. The skin is mostly smooth, and forms a broad glandular fold which extends from the eye to the groin. The upper parts are beautiful magenta red, with a purplish streak beneath the lateral folds; the under parts are yellowish white, with minute grey specks. Red or pink colours, and the lateral folds, occur also in most of the other members of this family, for instance in the Indian genus _Calluella_.

SUB-FAM. 3. GENYOPHRYNINAE.–_With very small teeth on the anterior portion of the lower jaw._

_Genyophryne thomsoni._–Pupil horizontal. Tongue oblong and entire. With teeth on the palatine bones, and a serrated transverse dermal ridge in front of the oesophagus. Sternum cartilaginous. Precoracoids absent. Sacral diapophyses moderately {237}dilated. Tympanum hidden. Head large and much depressed. Heel with a triangular dermal flap. The smooth skin is pink brown above, with blackish marks; a light line extends on each side from the eye along the back. Under parts black. About 32 mm. in length. Sudest Island, between New Guinea and the Louisiade Archipelago.

FAM. 7. RANIDAE.–Frogs, in the true sense, are all well diagnosed as _Firmisternia, with cylindrical sacral diapophyses_. According to the presence or absence of teeth in the jaws they can be subdivided as follows:–

SUB-FAM. 1. CERATOBATRACHINAE, with teeth in the upper and in the lower jaws. The sole representative is the genus _Ceratobatrachus_.

SUB-FAM. 2. RANINAE, with teeth in the upper, but none in the lower jaw. These are the Ranidae of Boulenger in the Catalogue of Batrachia Salientia.

SUB-FAM. 3. DENDROBATINAE, without teeth in the upper and lower jaws.

SUB-FAM. 1. CERATOBATRACHINAE.–Teeth present in both jaws. Those of the lower jaw, between 20 and 30 in number in _Ceratobatrachus_, the only genus, are nearly all inserted upon the articular bone; only 2 or 3 are carried by the dentary element, which, although large, enters into the formation of the upper border of the jaw at the anterior end only. In the small extent of the share of the dentary in the formation of the edge of the lower jaw, and in its anterior "toothlike" process, _Rana adspersa_ of Africa bears unmistakable resemblance to this genus. The tongue is deeply notched, and free behind. Pupil horizontal. Vomers furnished with teeth. Tympanum distinct and large. Precoracoids present. Omosternum and presternum with a bony style. Sacral diapophyses cylindrical. Fingers and toes free, with swollen tips. Outer metatarsals united. Male with two internal vocal sacs.

_G. guentheri_, Solomon Islands, the only species, has an enormous mouth and a triangular head not much smaller than the rest of the body. The skull is furnished with prominent ridges and a small curved spine at the angle of the jaws. The hind-limbs are rather short. The skin of the upper parts shows linear ridges, variously arranged; that of the belly is granular. A triangular dermal flap on the tip of the muzzle, one on the {238}upper edge of the eyelids, others on the heel and above the vent. The colour and markings are very variable, the ground-colour is yellowish to pink, brown, grey or olive, with darker and lighter markings. Total length of the males 3 inches, of females 3½ inches.–Guppy, the discoverer of this peculiar creature, remarks that "horned Frogs are very numerous in these islands, and so closely do they imitate their surroundings in colour and pattern, that on one occasion I captured one by accidentally placing my hand on it when clasping a tree."

SUB-FAM. 2. RANINAE.–The vertebrae are procoelous and devoid of ribs. The precoracoids are always present and ossified from the clavicles, and are parallel with the much stronger and ossified coracoids. The omosternum usually possesses a bony style, but in the Indian genera _Nannobatrachus_ and _Nannophrys_ and in _Phyllodromus_ of Ecuador it remains cartilaginous, and in _Colosthetus_ of Colombia it is absent. The metasternum also possesses a bony style, but it remains cartilaginous in the Indian genera _Oxyglossus_, _Nannophrys_, _Nannobatrachus_ and _Phyllodromus_, in the last two genera rather reduced and slender, while in the Ecuadorian and Colombian genera _Hylixalus_, _Prostherapis_ and _Colosthetus_, it is reduced to a membranous piece. In quite a number of genera the normal number of phalanges is increased by one owing to the intercalation of an extra phalanx between the terminal and the otherwise penultimate phalanx.[104] This is the case in all the species of _Cassina_, _Hylambates_, _Rappia_, _Megalixalus_, _Rhacophorus_, _Chiromantis_, _Ixalus_ and _Nyctixalus_, but it is doubtful if all these genera are thereby more nearly related to each other than to the rest of the Raninae. The structure of the tips of the fingers and toes exhibits more variety. The terminal phalanges are mostly simple, with slight swellings at the ends, or they are Y- or T-shaped in conformity with more or less developed adhesive discs; in the African genus _Hylambates_ only they are claw-shaped, as in the Hylidae.

_Gampsosteonyx batesi_, recently described by Boulenger from the Gaboon, shows a unique modification of the terminal phalanges of the second to the fifth toes. They are transformed into sharp and curved claws, like those of a cat, but instead {239}of horny sheaths, it is the bone itself which is thus sharpened and perforates the skin, an anomaly reminding us of the ribs of _Triton waltli_. Total length of the type-specimens, about 3 inches.

Adhesive discs are common, and are best developed in _Rhacophorus_, _Ixalus_, _Rappia_, and _Megalixalus_. In the Neotropical genera, excepting _Colosthetus_, the discs are very peculiar, being provided on the upper side with leathery scales which are separated by a fissure. The fourth and fifth metatarsals either diverge and are connected by a distinct web, or they lie close together with only a groove between them, or lastly they appear externally united.

The tympanic disc is very variable, large, small or quite hidden. Vomerine teeth are present or absent. The pupil contracts into a horizontal slit except in some Palaeotropical genera. The tongue is universally free behind, mostly deeply notched, and can be well protruded; only in the Indian _Oxyglossus_ and in the Neotropical genera, excepting _Hylixalus_, its posterior margin is entire.–There are terrestrial, arboreal, and aquatic members in this large sub-family. The geographical distribution of the Raninae, which comprise about twenty genera with at least some 270 species, is almost entirely Arctogaean. None, with the exception of three species in the Papuan subregion, occur in the Australian region; and only four genera, with one or two species each, inhabit the tropical Andesian district, the {240}remainder of South America being without any Raninae. All the species of the whole Periarctic region belong to the genus _Rana_ except in Eastern Asia, where the closely allied genus _Rhacophorus_ occurs also. The entire sub-family of Raninae is, in its fulness and diversity of development, essentially Palaeotropical.

Many of the genera, even in the present more liberal sense as interpreted by Boulenger, are based upon unimportant characters, and in reality run into each other. This is for instance the case with _Rana_ and _Rhacophorus_.

The following tabular arrangement is merely a key for determination and does not necessarily express relationships. The presence or absence of vomerine teeth is a character easily ascertained, but it separates closely allied genera, for instance, _Rhacophorus_ from _Ixalus_ and _Micrixalus_ from Rana.

The genera with extra, interpolated phalanges are marked *.

KEY FOR THE DETERMINATION OF THE GENERA OF RANINAE.

I. Pupil vertical.

_A_. With vomerine teeth.

_a_. Omosternum very slender and cartilaginous. Small discs. India
and Ceylon, 3 species .......... _Nannobatrachus._

_b_. Omosternum with a bony style.

α. Outer metatarsals webbed. Small discs. South India, 2 species
.......... _Nyctibatrachus._

β. Outer metatarsals close together. Africa.

Fingers and toes with interpolated phalanges.

Without terminal discs. 2 species .......... _Cassina._*

With discs supported by claw-shaped phalanges, 10 species
.......... _Hylambates._*

Fingers and toes without interpolated phalanges; without discs.

Toes webbed .......... _Trichobatrachus robustus_,
p. 271.

Toes free, with sharp claws .......... _Gampsosteonyx batesi_,
p. 272.

_B_. Without vomerine teeth. Discs well developed. Outer
metatarsals united. Tropical Africa and Madagascar, 7 species
.......... _Megalixalus._*

{241}II. Pupil horizontal.

_A_. With vomerine teeth.

_a_. Outer metatarsals webbed together.

Fingers free, toes webbed .......... _Rana_, p. 249.

Fingers and toes more or less webbed. Always with discs ..........
_Rhacophorus_,* p. 245.

Two fingers opposed to the others. Africa ..........
_Chiromantis_,* p. 244.

_b_. Outer metatarsals united, or separated by a groove only.

Omo- and meta-sternum with a bony style .......... _Cornufer_,
p. 243.

Omo- and meta-sternum slender and cartilaginous.

Ceylon, 2 species .......... _Nannophrys._

Mozambique .......... _Phrynopsis boulengeri._

_B_. Without vomerine teeth.

_a_. Palaeotropical.

α. Tongue narrow and entire. No discs. Outer metatarsals webbed.
India, 3 species .......... _Oxyglossus_.

β. Tongue oval, feebly nicked. Large discs. Solomon Islands
.......... _Batrachylodes vertebralis._

Karin Hills .......... _Phrynoderma asperum._

γ. Tongue deeply notched. Outer metatarsals united by a web.

Discs none or very small.

Africa, 3 species .......... _Phrynobatrachus._

Borneo .......... _Oreobatrachus baluensis._

With regular discs.

Number of phalanges normal. India, 5 species ..........
_Micrixalus._

With an extra, interpolated phalanx. India, 18 species
.......... _Ixalus._*

Two fingers opposed to the others. Karin Hills ..........
_Chirixalus doriae._*

δ. Tongue heart-shaped. Outer metatarsals united.

Fingers and toes free, tips blunt. Africa, 8 species ..........
_Arthroleptis_, p. 242.

Fingers and toes more or less webbed, with regular discs. Africa
and Madagascar, 23 species .......... _Rappia._*

{242}_b_. Neotropical. Metasternum small, cartilaginous or
membranous. With discs.

1. With a pair of dermal scales on the discs. Omosternum with a
bony style.

Tongue heart-shaped. Ecuador, 2 species .......... _Hylixalus._

Toes free. 5 species .......... _Phyllobates_, p. 242.

Tongue entire. Ecuador and Colombia, 3 species ..........
_Prostherapis._

Omosternum cartilaginous. Ecuador .......... _Phyllodromus
pulchellus._

2. Discs without scales. Omosternum absent. Colombia ..........
_Colosthetus latinasus._

_Phyllobates._[105]–This is one of the few Neotropical genera, and like nearly all of these has peculiar adhesive discs on the fingers and toes, each disc bearing on its upper surface two dermal scales. The tympanum is distinct. Vomerine teeth are absent. The general appearance of the five species is that of tree-frogs. One species, _Ph. bicolor_, yellowish above, dark brown beneath, lives in Cuba. The others inhabit Central America and Venezuela. They seem to have peculiar nursing habits. _Ph. trinitatis_ of Venezuela and Trinidad carries its tadpoles on its back, on to which the young fix themselves by means of their suckers. Nothing is known about their breeding habits, for instance whether the young are hatched on the back, or, as seems more likely, if the parents (the specimen described by Boulenger[106] is a male) only give their offspring a temporary lift in order to convey them from a drying-up pool to a healthier place. It is remarkable that several species of Dendrobatinae, which inhabit the same countries, have precisely the same habits.[107]

_Arthroleptis._–Slender and long-limbed little frogs, about one inch in length. The fingers and toes are free, very slender, and end in slightly dilated tips, the supporting phalanges being simple. The tympanum is variable. The skin is smooth or finely granulated. The colours are inconspicuous, brown or grey tones usually prevailing. About ten species are known, mostly {243}from Continental Africa, a few from Madagascar and the islands in the Indian Ocean.

_A. seychellensis._–Brauer[108] has discovered the mode of nursing of this frog. He found a specimen of _A. seychellensis_ which carried nine tadpoles on its back, in the month of August, in the Seychelles, about 1500 feet above sea-level, upon an old tree-fern. The little ones were already provided with long tails, the hind-limbs were partly free, the fore-limbs still covered by the skin, and they held on by their bellies; not, like the young of _Phyllobates_, by their "suckers." Another specimen carried young which were still further developed. He also found an old frog, near which was lying a little heap of eggs, not enveloped in a common mass of jelly. The old frog escaped, but the eggs were taken care of in a vessel with moist sand at the bottom. By the following morning the eggs were hatched and the tadpoles were clinging by their bellies on to the walls of the glass. Brauer concludes that the young, when hatched, creep on to the parent's back, he or she waiting near the heap of eggs until the latter are ready. Curiously enough, he did not find out the sex of the nurse, nor are we told if the young are taken to the nearest water to finish their metamorphosis, or if they remain upon the parent's back until they hop off as baby-frogs. The yolk is very large. When the four limbs are already developed, the gill-cavity possesses no gills and no outer opening; and since the lungs are only just beginning to sprout, the tadpole must needs breathe by means of its skin. The jaws have no horny coverings. The adults live on the ground between moist leaves, and eat chiefly termites.

_Cornufer_, with about twelve species, is an essentially Austro-Malayan and Polynesian genus, but one species, _C. johnstoni_, has been found in the Cameroons. The fingers and toes are free, and their T-shaped phalanges support adhesive discs. The tympanum is distinct. The general shape is frog-like, usually with slender and very long hind-limbs and toes, the discs of the latter being much smaller than those of the fingers. The coloration is dull, mostly brown, more or less marbled, whitish below. The {244}upper eyelid of some species, _e.g._ of _G. unicolor_ of New Guinea, has a small tubercle, hence the generic name. The skin of the back is glandular and granular, forming slight folds on the back and on the sides of the head in some species. The male has one or two internal vocal sacs.

_C. corrugatus_ is one of the most widely distributed species, inhabiting the Philippines, New Guinea, and Duke of York Island. The granular skin forms longitudinal folds on the back, one of which reaches from the eye to the shoulder. Brownish above with darker markings, below yellowish, with or without brown spots on the throat.–Three species inhabit the Fiji Islands.

Of _C. solomonis_ of the Solomon Islands little is known about the propagation, although the large size of the egg, which measures 5 mm. in diameter, suggests that the young undergo most or the whole of their metamorphosis within the egg.

_Chiromantis_ is distinguished by the peculiar arrangement of the fingers, the first and second being opposed to the others; their terminal phalanges are obtuse and support small knobs or discs. The general shape is that of a frog with long and slender hind-limbs. The tympanum is distinct.

_Ch. xerampelina_, the type-species, was discovered by Peters at Mozambique; it is a middle-sized frog, about 2 inches in length, brown above with reddish spots on the sides; the male is devoid of vocal sacs.

_Ch. petersi_, a native of East Africa, differs from the preceding by the possession of an internal vocal sac. _Ch. rufescens_ = _guineensis_ shows very little of the typical grasping arrangement of the fingers; the two inner ones are separated from the two outer fingers by a wide gap, but they all lie in the same plane, are much webbed and possess large discs, so that by the latter two characters a link is formed with _Rhacophorus_, to which the present genus is closely allied. Total length about 2½ inches.

Buchholz[109] has observed the peculiar breeding habits of this rather large, brown, and slender tree-frog in the Cameroons. In the month of June he found on the leaves of a low tree, standing in the water, a white foamy mass, like the froth of a broken egg, containing a number of newly hatched larvae and quite transparent eggs. Within three or four days this mass became {245}fluid, and the larvae, provided with external gills and a long tail, swam about in the slime. In the natural course of events the larvae are probably washed down into the water by the rain. He found that the female deposits the eggs in the foamy mass at night, during the months of June and July, on various kinds of trees, either between the roots or in a cavity formed by gluing together several leaves, sometimes 10 feet and more above the water, or near the margin. On one occasion the mother was seen sitting upon the foamy mass, clasping the same with its four limbs.

_Rhacophorus._–This large genus, containing more than forty species, has a curious distribution. At least one dozen species are found in Madagascar, eight or nine in Ceylon, the rest in Southern India, the Himalayas, the Malay Islands and Philippines, extending northwards through China and Southern Japan. Therefore this genus, with the three species of the African _Chiromantis_, extends over the whole of the Palaeotropical region. The generic name has reference to the possession by many species of little dermal flaps, especially at the inner side of the heel, and it has nothing to do with the parachute-like use of the hands and feet of certain species, to be mentioned presently.

The terminal phalanges are generally bifurcated, rarely obtuse, and support well-developed adhesive discs. The fingers and toes are webbed to a variable extent. The two outer metatarsals are likewise connected by a web. The tympanum is distinct. The general appearance is that of tree-frogs, and many of them are green. The males have one or two internal vocal sacs. Not all the species have dermal appendages. _Rh. maximus_, for instance, the largest of all, living in the Himalayan forests, has none. A heel-flap occurs in some half-dozen Indian species; and _Rh. madagascariensis_ has these flaps on the heels and on the elbows. Some have queer little lappets above the vent, or on the edges of the arms and legs; in others the bend of the arm is fringed. The small size of these appendages, in comparison with the webs and discs, makes them practically useless so far as increase of surface is concerned, and they have most likely some other, although unknown meaning, especially the flaps over the vent. Lastly, in the majority of species the fingers are not more than half-webbed, or even less, and in a few only, the webs reach down to the discs.

{246}Several species of this genus are remarkable for two reasons. First, the great enlargement of the fully-webbed hands and feet, which are then used as parachutes; secondly, the mode of propagation.

Greatly exaggerated notions are, however, entertained about the parachutes, ever since Wallace's description[110] of the first "flying frog." The creature was brought to him in Borneo by a Chinese workman. "He assured me that he had seen it come down, in a slanting direction, from a high tree, as if it flew.... The body was about four inches long, while the webs of each hind-foot, when fully expanded, covered a surface of four square inches, and the webs of all the feet together about twelve square inches."

The species in question is _Rh. pardalis_, an inhabitant of Borneo and of the Philippine Islands. Specimens from Wallace's Collection are in the National Collection and the largest specimen {247}shows the following measurements. Total length 6.5 cm. or 2½ inches, not 4 inches.

Area covered by one fully-expanded hand 3.4 square cm.
" " " foot 6.0 " "
–––
9.4 square cm.

_i.e._ for the four limbs 18.8 square cm. = about 3 square inches, and not 78 square cm. or 12 square inches. By some unfortunate oversight Wallace must have mixed up the total expanded area with that of the four hands and feet! In Brehm's _Thierleben_ the 78 square cm. have increased to 81 cm., and the artist has in the somewhat larger species _Rh. reinwardti_ improved upon this, and has produced a truly startling picture by a further exaggeration based upon the figure given by Wallace.

_Rh. reinwardti_ lives in the forests of the mountains of Java and Sumatra. It reaches 3 inches in length, and is grass-green above, yellow below. Younger specimens are further adorned with large blue patches on the webs of the hands and feet and behind the armpits. Besides the flap on the heel and the curious cutaneous fringe on the forearm, suggestive of an incipient flying-membrane, the skin forms a projecting fringe on the inner side of the fifth toe and a transverse flap above the vent.

Of _Rh. leucomystax_, Annandale, who accompanied the Skeat Expedition to Malacca, gives the following account:–"This frog, which is called by the Malays of Lower Siam either 'Berkata Pisang' (banana-frog) or 'Berkata Rhumah' (house-frog), lays its eggs either on leaves of branches overhanging the water, or on the mud surrounding buffalo-wallows. The ova are enclosed in a round mass of yellow froth, which afterwards becomes steel-grey, about as large as a cricket-ball. Should they be placed judiciously in a position sheltered from the sun, the tadpoles may either hatch, and reach a considerable degree of development, before the mass is washed into the water, or the froth may be melted almost as soon as it is formed and the eggs be carried into a pool by a shower of rain. Very often, however, the whole mass is dried up by the heat of the sun before the rain comes. During the breeding season, which seems to occur as often as the land is flooded under the trees, for I have never seen the eggs of this frog on the bank of a river, the {248}males croak loudly, producing a sound which can hardly be distinguished from the chattering of the large black and yellow squirrel, _Sciurus bicolor_."

These arboreal frogs have a peculiar mode of nursing the young and taking care of the eggs. _Rh. maculatus_ of Ceylon, Malacca, etc., and _Rh. schlegeli_ of Japan, lay their eggs in a foamy mass, the size of a fist, on the margins of ponds, and the whole process has recently been described by Ikeda.[111] He observed the Japanese _Rh. schlegeli_ depositing the eggs in soft, muddy ground covered with grass, and in wet, muddy banks of paddy-fields, ponds, and similar localities near Tokyo. Sometimes they are deposited between the leaves of trees, near the ground. The breeding season extends from the middle of April to the middle of May. Towards the evening the female, bearing the much smaller male on her back, retires underground for the deposition of the eggs. The spots chosen are 10-15 cm. above the surface of the water; the female digs a spherical hole 6-9 cm. wide. Sitting thus concealed underground, the frogs assume a dark colour and the spawning takes place during the night, whereupon the parents leave the nest. The eggs are enveloped in a white mass of jelly full of air-bubbles, the whole frothy lump looking like the well-beaten white of a hen's egg, with the yellowish eggs scattered through it, and measuring some 6 cm. in diameter. The air-bubbles are 2-3 mm. large. The froth is originally very elastic and sticky, but it gradually sinks down, becomes liquid and ultimately runs out of the hole. It is produced in the following peculiar manner. During and after the deposition of the eggs the female puts her feet upon the sticky jelly, part of which adheres and is then pulled out as a thin, transparent membrane stretching between both feet. The latter are then thrust backwards, the membrane is folded downwards and becomes a vesicle of 5 to 10 mm. in width. By repeated working of the limbs the successively formed bubbles are trodden and kneaded into froth, which ultimately surrounds and at the same time separates the eggs.

The female of _Rh. reticulatus_ of Ceylon attaches the eggs, about twenty in number, to the under surface of her belly, on the skin of which they leave little cellular impressions. What becomes of the tadpoles is not known.

{249}_Rh. leucomystax_ is found in the Malay Archipelago, Farther India, and the Philippine Islands.

S. S. Flower[112] found the tadpoles about Singapore, from January to April, in small ponds and in rain-water butts. The spiracle lies on the left side, directed backwards and upwards, nearer the anus than the end of the snout. The anus opens on the right side. Exceptionally large tadpoles measured 46 mm. in total length, the recently transformed young only 14-18 mm.

"A cheerful little frog of most graceful build. It comes out from its hiding-places shortly before sunset, and remains abroad all night. The males are easily found as they sit on shrubs or trees, or on the edges of the rain-water butts under the verandahs of the houses, and from time to time utter a single, rather musical, short croak. In March and April they can be found both by day and night in embrace, in the ponds. This species changes both its colour and markings very rapidly and frequently, but dark bands across the legs can always be more or less distinguished; the lower parts are some shade or other of buff, but the principal variations of the upper part are as follows: pale bronze, either uniform or with four longitudinal dark-brown or black lines; uniform, almost orange, bright bronze; chocolate, with darker mottling; pale brownish green or olive, with irregular dark spots; yellowish green, mottled with darker or brown." The females are considerably larger than the males; the largest male caught was 48 mm. from snout to vent, and the largest female 68 mm.

_Rana._–The following combination of characters should be a sufficient diagnosis: pupil horizontal; tongue deeply notched and free behind; vomers with teeth; fingers free, toes webbed, fourth and fifth metatarsals diverging and webbed together.

In conformity with the great number of species and the wide distribution of this genus some of the organs vary considerably, indeed so much so that many of these modifications have been deemed sufficient to be of generic importance. Fortunately the species are so numerous that these characters mostly form an uninterrupted series from one extreme to the other.

The terminal phalanges are mostly simple and pointed; sometimes transversely dilated or T-shaped, according to the presence of more or less developed discs. Such discs are, for {250}instance, present in the Malay species _R. erythraea_ and _R. chalconota_ and in the Indian _R. corrugata_. The tympanum occurs in every stage from a conspicuous, free disc to being quite hidden by the skin. The vomerine teeth either form a pair of tiny, mostly transverse rows, between the choanae, or they are arranged in two oblique series which extend beyond the hinder edges of the choanae.

The vocal sacs vary greatly. Many species, e.g. _R. agilis_, have none at all. Most species have a pair of internal sacs, and in comparatively few, about a dozen, these sacs have become external, a feature which indicates no relationship of the species thus distinguished, for instance the European _R. esculenta_, the Japanese _R. rugosa_, the Indian _R. hexadactyla_, _R. cyanophlyctis_ and _R. Chloronota_, the Bornean _R. glandulosa_, the African _R. oxyrhynchus_ and _R. mascareniensis_, the Mexican _R. montezumae_. In _R. esculenta_, and perhaps in a few others, even the female has some traces of these otherwise male organs, indicated by slit-like folds of the outer skin below the angles of the lower jaw.

Nuptial excrescences on the inner metacarpal tubercle and on the inner fingers of the male are common; they reach their greatest development in the Himalayan _R. liebigi_, the male of which is "remarkable for the extreme thickness of its arms, the inner sides of which are studded with small conical black spines, each supported on a rounded base produced by a swelling of the skin. A large patch of similar spines exists on each side of the breast."[113]

Specific glandular complexes in the skin are mostly restricted to a pair of lateral or dorso-lateral folds; they are often absent, but a few species, e.g. _R. glandulosa_ of Borneo, _R. temporalis_ of Ceylon, _R. elegans_ and _R. albolabris_ of West Africa, have a pair of large flat glands at the base or inner side of the arms.

All the species of _Rana_, except those in the Solomon Islands, spawn in the water, where the development of the tadpoles takes its course. Those of some Indian species, notably _R. alticola_ and _R. afghana_ of the Himalayas, and _R. curtipes_ of Malabar, are very peculiar, being provided on either side of the shoulders with a large oval parotoid-like gland, well defined and crowded with pores; _R. alticola_ possesses in addition an unpaired, sharply {251}marked glandular complex on the top of the root of the tail, or rather upon the future coccyx. These complexes gradually disappear with age.

The genus _Rana_, with about 140 species and subspecies, is distributed over the whole of Arctogaea so far as this is available for Amphibian life, while there are only a few stragglers in Notogaea, namely, a few species in Ecuador and in the Peruvian or Upper Amazon district. None exist in the rest of the Neotropical region, including the Antilles, and practically none in Australia; but _R. arfaki_ and _R. papua_ inhabit New Guinea and the northern corner of Australia, _R. kreffti_ the Solomon Islands. A few species are restricted to Madagascar, and a few others live there and on the continent of Africa.

So far as number of species is concerned, the home of the genus _Rana_ is the Palaeotropical region; about one dozen (some of them with a very wide range) live in the Palaearctic sub-region, scarcely more in the Nearctic sub-region, and a few in Central America.

_R. temporaria_ (the common European Brown Frog or Grass-frog).–The tympanum is distinct, two-thirds the diameter of the eye in size. The first finger is slightly longer than the second, which is shorter and weaker than the others, whilst the fourth is the longest. All the fingers are quite free. When the hind-limbs are laid forwards along the body, the ankle-joint reaches to a point between the eye and the tip of the snout. The five toes, which are about half webbed, increase in length from the first to the fourth, while the fifth is about equal to the third. The sole of the foot has a small, blunt, inner metatarsal tubercle; the outer one is scarcely visible. The skin is smooth, always moist, owing to the minute mucous glands; but a series of larger glands forms a pair of folds along the upper sides of the back; beginning behind the eyes they converge slightly beyond the shoulders, diverge a little in the sacral region, and converge again towards the vent. Another, much feebler, Λ-shaped ridge lies between the shoulders.

The male has two internal vocal sacs, which, when in use, bulge out the skin of the throat beneath the angles of the mouth like a pair of globes. It is further distinguished from the female by the stronger muscles of the arms and by a pair of swollen pads on the inner side of the first finger. During the pairing {252}season these pads are enlarged into cushions covered with black horny rugosities.

The iris is golden, with dark specks. The coloration is, generally speaking, brown above, with black-brown irregular spots, especially on the sides of the body, and with cross-bands on the legs. The under parts of the male are white or pale yellow, with a bluish tinge on the throat, while the female is more yellow instead of white, inclining to orange. In both sexes the under parts are mostly spotted with darker colours. A large dark-brown patch, extending from behind the eye over the tympanum towards the shoulder, is always present and has given this frog its specific name. Otherwise the coloration varies considerably; more or less according to the locality and nature of the surroundings, and to individual variation and temporary change of colour.

Some specimens are almost spotless above and of a rich brown, or almost yellow colour, the spots being restricted to the sides below the lateral folds. Others have very few spots, but these are then arranged in two interrupted streaks on the back. The under parts, especially the flanks, may be lemon yellow instead of whitish, and the darker markings may be almost absent. Boulenger has figured a beautiful specimen, almost orange red, with red spots and vermiculations on the yellow under surface. I have found similar red specimens of unusually striking appearance between Berlin and Spandau in a forest-glade, through which run little streams with banks of red ferruginous soil. Specimens which live in woods with rich black soil are often very dark, all the brown and reddish tints being absent. The variations are, however, really endless, and it is difficult to find two individuals exactly alike, even amongst a great number collected in the same locality. Moreover, they change colour. Warmth makes them paler, cold causes the chromatophores to expand and the whole frog appears darker. During the breeding season the males assume a delicate bluish hue, especially on the throat, but this film quickly fades away when they are taken out of the water. It is caused by the swelling of the cutaneous lymph-spaces which extend their ramifications into the epidermal layer, and it is not a question of pigmentation or of chromatophores, but a case of interference-colours, blue being frequently the result of the light passing through a cloudy, colourless, but not {253}quite transparent and thin stratum, in this case the turgid epidermis.

The habits of the Grass-frog are essentially terrestrial. It spends most of its time on land, preferably in damp places, but local fashion permits of a great deal of freedom, as these frogs are sometimes found not only in very wet, naturally irrigated places, but also in the water itself. However, the Grass-frog when pursued rarely takes to the water for safety. It trusts to flight, first by a few long and fast jumps, and then to concealment by squatting down between grass, under leaves; it rarely creeps into a hole, even if there be one near. The jumps soon become shorter and shorter after a few dozen repetitions. It swims well, but cannot climb. The food, which consists chiefly of insects, snails, and worms, must be moving to excite interest; then the frog, whose favourite position is half squatting, half supported by the arms, erects itself, and, facing the insect, turns round upon its haunches, adjusts its position anew by a shifting of the legs, and betrays its mental agitation by a few rapid movements of the throat. All this time the prey is watched intently until it moves; then there follows a jump, a flap of the tongue and the insect is seen no more. As a rule these frogs do not crawl, they jump or hop, even whilst stalking, and this takes place at any time of the day; in fact they are very diurnal, although they become more active towards the evening. When caught they are at first very wild and, like all true frogs, very impetuous, committing acts of astonishing stupidity without any apparent sense or appreciation of distance or height. The captive will not only jump off the table, whilst a toad stops at the edge and looks carefully down, but without hesitation he jumps out of the window, regardless of the height above the ground. This is due to sheer fright; he loses his head. When at large in his native surroundings, nothing will induce him, although hotly pursued, to commit suicide by jumping down a precipice. But all this wildness calms down wonderfully soon. The captive no longer dashes his head against the glass, he does not struggle or twist when taken up; on the contrary, he makes himself at home, watches your coming with intense expectation, and without hesitation accepts the proffered mealworm, maggot, butterfly or earthworm; in short, he shows what a jolly and intelligent fellow he really is.

{254}The Grass-frog has many more obvious enemies than perhaps any other Amphibian, and it is not even slightly protected by any appreciable poisonous secretion. Nevertheless it is extremely common. A whole host of birds eat it–for instance, buzzards, harriers, and above all storks. Foxes, polecats, and stoats are not averse to it, and the Grass-snake derives its main sustenance from it. In fact the enemies of the little frog are legion, one of the worst being Man. In France, Italy, and other parts of the Continent, the skinned fleshy hind-limbs are turned into a by no means disagreeable ragoût, or into dainty morsels when fried in butter and encrusted with bread-crumbs. This frog, together with its cousin the Water-frog, also suffers from the distinction of being one of the chief martyrs to science. Perhaps the story is true that Galvani was led to his investigations into animal magnetism and electricity by observing that the legs of a number of skinned frogs, strung up by his wife upon the bronze railings of the balcony, jumped whenever the scissors, which cut off the feet, touched the other metal. Frogs have suffered ever since. Easily procured and of a convenient size, they are used in every biological laboratory, and the young student is supposed to be initiated into the mysteries of Vertebrate structure by the careful dissection and study of this, the worst of all the so-called types. Next to Man there is no animal which has been studied so minutely, and has had so many primers and text-books written on it, as this frog. In spite of all this it is very little understood, thanks to its rather aberrant and far from generalised structure.

However, the frog, by reason of its fertility, holds its own. Early in the year, sometimes while there is still ice and snow, the frogs leave their hibernating places (mostly holes in the ground, under moss, or in the mud), and they begin to pair in standing or slowly flowing, mostly shallow, waters.

They are not always very careful in the selection of the spawning locality, many of them lay their eggs in a ditch, or even in the shallowest puddle, which is sure to dry up, and thus to cause the destruction of the whole brood. This carelessness is all the more surprising when there are large pools or lakes in the immediate vicinity, perhaps only one hundred yards to the other side of the road. The Natterjack is, by the way, equally careless, while other toads and the tree-frogs are very circumspect.

{255}

Both sexes can croak, and this sound is frequently produced under water; but there are no regular concerts, although many collect in the same pond or spring, which is perhaps the only suitable place for miles around. The male puts its arms around the chest of the female, behind her arms, and the embrace is so firm that nothing will induce him to loosen his hold. The process becomes an involuntary reflex-action, a cramp which may last for days, or even for weeks, if sudden cold weather sets in, until the female is ready to expel the eggs, an act which is quick and soon over. The usual time of spawning in Middle Europe is the month of March, earlier in warm, later in cold seasons; in southern countries, February or even January, but in Norway not until May. Although the males of this species are not more numerous than the females, and therefore should be able to mate without much trouble, their ardour is so great that they occasionally get hold not only of the wrong kind of frogs, but of toads or even fishes, and, if taken off by force, they fasten on to anything else, a log or on to your own fingers. The eggs measure 2-3 mm. in diameter, are black with a whitish spot on the lower pole, number from 1000 to 2000, and sink at first to the bottom. Their gelatinous cover soon swells to a large globe more than 10 cm. in width, and the whole mass, as large as a man's head, floats on the surface, often stained with mud and other impurities. During the cold weather which often prevails in the spring, the dark brown larvae are slow in their development; and provided with rather large branched external gills and a well-developed tail, they wriggle about in the dissolving slime for three or four weeks. Fischer Sigwart[114] has timed and measured them as follows.–The eggs were laid on the 10th of {256}March. On the 15th the larvae were 4 mm. long and began to leave the eggs. On the 19th they measured, body 4, tail 9, total 13 mm.; on the 5th of April 10, 16, and 26 mm. respectively. On the 13th of May they were 40 mm. long and the hind-limbs appeared; the fore-legs burst through on the 25th, when the tadpoles had reached their greatest length, namely 45 mm., the body measuring 15 mm. On the 31st of May they left the water, still provided with a rather long tail of 20 mm., the total length being reduced to 35 mm. The larvae of this set developed unusually fast, perhaps owing to artificial conditions. The whole development is, however, mostly finished in three months, so that the little stump-tailed baby-frogs swarm about well before midsummer, and have time enough to grow to the size of 20 mm. or ¾ inch before they begin to hibernate in October.

In higher localities and in northern countries the tadpoles are sometimes obliged to winter in the unfinished condition.

In spite of the unusually hot summer of 1899 I found plenty of tadpoles on the 10th of September in the tarns of the hills of North Wales, 1500 feet above the level of the sea; while thousands of little frogs, with and without stumpy tails, were hopping about in the surrounding bogs. The water of these tarns is always very cool. Cold and rainy weather set in by the middle of the month, and on the 26th the tadpoles, all rather small, measuring only 35 mm., with the four limbs developed, but still with a broad fin on the tail, had all settled down under stones at the bottom of the now very cold water, prepared for hibernation. A few were taken home and kept in a glass vessel with water, cool, but less so than that of their native tarns. Within two days they lost the fins on their tails; before the end of a week they left the water, and crawled on to the moss, and the tails were reduced to little stumps. By the 10th of October the metamorphosis was complete, the little frogs measured only 13 mm. in length and showed no desire to hibernate in the genial atmosphere of the greenhouse.

This species has a very wide distribution. It ranges from the west of Ireland to the islands of Saghalin and Yezzo, being found everywhere in the enormous stretch of intervening countries, practically the whole of Central and Northern Europe and the middle belt of Asia. Its most northern extent is the whole of Sweden and Norway. I have found it to the east of the {257}Dovrefjeld, at an elevation of 4000 feet, well-nigh the snow-line. In conformity herewith it ascends the Italian Alps up to 10,000 feet. The southern limit in Europe is the Cantabrian range and the hilly province of Galicia. In the rest of the peninsula, in Italy and Lombardy, Greece and Turkey, and on the Mediterranean islands it is absent.

_R. arvalis_ is often confounded with _R. temporaria_, as it differs from the latter only by the following characters. The snout is rather more pointed and is narrower; the inner metatarsal tubercle is large, compressed, and hard; the dorso-lateral glandular folds are more prominent and the belly is white and immaculate; lastly, it scarcely reaches 3 inches in length, a size which is not rarely surpassed by the other species. There are also some differences in habits. _R. arvalis_ prefers moist, boggy, open localities, and does not ascend beyond 2000 feet in Central Europe. It pairs as a rule later in the spring and the eggs are smaller, only 1½-2 mm. in diameter; they do not swell up so much, and the whole mass does not float but remains at the bottom of the shallow water. The coloration much resembles that of _R. temporaria_, and is likewise subject to much variation, except that the pale vertebral stripe is perhaps more common. This species is distributed over the whole of Central Europe, Russia, and Western Siberia, south of the 60th degree of latitude, living side by side with _R. temporaria_. Between the rivers Elbe and Rhine it becomes decidedly rare, and the latter river is practically its western boundary, while the Bavarian Alps and the Danube form its southern limits.

_R. agilis_ is still more frequently confounded with both the two former species. It differs from either by the absence of the two internal vocal sacs of the male, and by the decidedly longer hind-limbs, the tibio-tarsal joint reaching often a little beyond the tip of the snout. The inner metatarsal tubercle is as prominent as in _R. arvalis_. Total length up to 3 inches. The prevailing colour of the upper parts is rather yellow or pink-brown with few and small blackish spots; a Λ-shaped dark mark on the neck is often present, and the large dark patch on the temporal regions is always conspicuous. The under parts are white, inclining to lemon yellow on the flanks and thighs. The iris is golden yellow in its upper half, dark brown in the lower half.

{258}This species has a much smaller range than the first two:–from France through Middle and Southern Germany, Switzerland, and Lombardy to Hungary and Greece. The specific name refers to the quick and long leaps of this pretty, or rather delicately coloured frog, which prefers woods and wooded glens to large open places. Their voice differs much from the croak of the common Brown Frog, and agrees with that of _R. arvalis_, which is transcribed by Boulenger, who has kept them alive, as a rapidly uttered "co-co-co," or "cor-cor-cor." According to the same authority, the pairing takes place as in _R. temporaria_, but is of much shorter duration, the females usually resorting to the water only at night and when quite ready to spawn. Specimens in embrace are therefore seldom found in the daytime. The eggs resemble those of _R. temporaria_ in size, but they do not swell up so much and they do not float.

These three species of European brown frogs, difficult enough to distinguish, have of late been increased by three more, thanks to the sagacity of Boulenger. These latter inhabit South Europe, and the males all lack the internal vocal sacs.

_R. iberica_ has a very small range, namely the north-western portion of the Iberian peninsula, from the Tagus northwards into Galicia, but south of the main extension of the Cantabrian chain. The rest of the Peninsula south of these mountains has no brown frogs, the only species of _Rana_ being _R. esculenta_. _R. iberica_ is rather local, being restricted to those hilly and mountainous districts which are well watered. A favourite haunt is the numerous streams in the wooded parts of the Serra Gerez, the red, disintegrated granite of which suits this little, extremely active, and reddish frog to perfection. The prevailing ground-colour varies according to the district, from pale to dark reddish or orange brown, with red specks and larger, dark brown spots, which in some specimens begin with the Λ-shaped mark between the shoulders. Dark spots on the flanks are very variable; the hind-limbs show the usual darker cross-bars, and the temporal region has the conspicuous dark patch. The ground-colour of the under parts is whitish, suffused with a pink tinge, and the throat is much speckled with brown; the toes are pink. The size of this pretty frog amounts to 2 inches. The breeding time is the month of March. When caught and squeezed they emit a slight "co-co-co."

{259}_R. graeca_ inhabits Italy and the Balkan peninsula from Rosina to Morea, together with _R. agilis_, from which it is very difficult to distinguish except that it is a little smaller, remaining below 2½ inches, and is generally more uniformly pale grey brown to yellowish and pinkish brown above, with scarcely any, or only a few, small dark specks on the back and limbs. The temporal patch is likewise paler than in the other species. The flanks are spotless, their colour gradually passing into the light buff of the under parts, which are more or less marbled with grey. The iris is golden, speckled with dark brown.