in the Atlantic States. It is brownish-yellow above, with a black lateral
line extending from the eye to nearly the end of the tail. The under parts
are bright yellow. It lives on land, in damp places, concealed during the
daytime under stones or old trees, whence it emerges after a rain or in the
dusk of evening.
According to H. H. Wilder,[49] "the eggs are deposited in May and June in a
single layer upon the lower side of submerged stones, each batch containing
30 to 50 eggs. The stones which are suitable for this purpose must be in
the form of an arch, allowing the water to flow beneath. They are generally
in the more rapidly flowing portions of the brook, but the depth of water
must be such that the eggs are at all times entirely submerged. They are
attached to the stone by gelatinous threads, proceeding from the outer
envelope, and although they are generally contiguous, they {105}are each
attached separately." The eggs are holoblastic. The larvae hatch early and
continue for a long time in the larval state, probably two or three years.
_S. porphyriticus_ s. _salmoneus._–Yellowish-brown or purplish-grey above
with tiny darker dots and markings. The sides of the body are
salmon-coloured, with a tinge of yellow. The under parts are whitish,
turning into salmon-pink on the tail. This beautiful newt reaches about 6
inches in length and has a very moist, slimy skin, which, combined with the
lively motions of the creature, make it as slippery as an eel. It is found
in the Alleghany range, from New York to Alabama.
Specimens which I am keeping prefer the wettest part of the cage, where
they lie concealed in the moss and mud, leaving their hiding-places at
night in search of insects. One of them escaped into the greenhouse and was
discovered after nine months, having established its permanent home in a
cleft between mossy stones: when the sweepings of a butterfly-net are
emptied near its hiding-place it peeps out and with a flash of its long,
forked, white-coloured tongue it secures its prey. Occasionally it goes
into a tank, when it swims with rapid, undulating motions, the limbs being
laid back and remaining inactive; it sometimes rises to the surface to emit
and to take in air, but, although mostly resting half in the water, upon a
rotten stump, it often lies for hours at the bottom without stirring. When
kept in dry surroundings, the skin soon dries and wrinkles, and the animals
show every sign of suffocation and general discomfort. The respiration of
this lungless species by means of rapid movements of the throat is very
limited, most of the necessary oxidisation of the blood being effected
through the skin.
_S. fuscus._–This, the only European species, is thoroughly terrestrial. It
is found in the mountains bordering the Gulf of Genoa, and in Sardinia. Its
total length remains under four inches. The smooth, very delicate and
easily broken skin is brown above, light below, and speckled with lighter
and darker markings. Below each nostril is a slight swelling, the remnant
of the cirri or balancers common to the young of many species. It lives in
shady surroundings, under stones, in old trees and in limestone-caves,
glued to the walls with spread-out toes, belly and tail, quietly waiting
for insects and spiders which it catches by flashing out the long tongue.
{106}According to J. Berg,[50] it keeps well in cool, moist and
well-ventilated places. It lives on flies, small beetles, and maggots; ants
are also taken at once, probably owing to their lively movements, but a few
minutes later the newts roll about in spasms and soon die. Towards the end
of March one of Berg's specimens gave birth to four young, which were 36
mm., or nearly 1½ inches long, and differed from the adult only by their
exceptionally large nostrils, thereby resembling the Mexican _Thorius_. The
little ones shot out their tongues about 10 mm., feeding on Aphides.
[Illustration: FIG. 20.–_Spelerpes fuscus_, showing the position and shape
of the partly and fully protruded tongue. The figure on the right side
shows the tongue and the skeleton of the hyoid apparatus. _B_, the
threadlike, elongated, first branchial arch; _H_, hyoid, in reality
attached by its outer end to the vicinity of the quadrate; _T_, tongue.
About × 2. (After Berg and Wiedersheim.)]
_Manculus._–The two species of this genus live in Carolina and Florida. _M.
quadridigitatus_ is a very slender, graceful little animal, about 3 inches
in length, the long and thin tail being considerably larger than the rest
of the body. Yellowish, minutely speckled with brown above and on the
sides, greyish-white below. Life entirely terrestrial.
_Plethodon._–About seven species in North America. This genus has given its
name to that of the subfamily, which might with more reason be called
Spelerpinae.
_P. glutinosus_ is slaty or bluish-black, with small whitish specks,
especially on the sides of the trunk, where they are large and often
confluent. The skin is smooth and shiny. Total length about 5 inches, half
of which belong to the tail. Holbrook considered this as one of the
commonest of the North American newts, and mostly widely distributed, from
Ohio to the Gulf of Mexico. It usually lives concealed under stones, but
prefers fallen trees, probably on account of the insects upon which it
{107}preys. When taken in the hand it gives off a great quantity of slime.
_P. erythronotus_ extends into Canada and is much smaller. Brown or grey
above, mostly with a broad, reddish-brown band over the head, back, and
tail. The under parts are white, with grey and brown specks.
_Autodax_ s. _Anaides_.–The large tongue is attached along the median line.
The jaws are furnished with few, but surprisingly large, knife-shaped
teeth, about ten in the upper and fewer in the lower jaw. The small teeth
of the vomers form a chevron-shaped series behind the choanae, those of the
parasphenoid stand in one elongated patch. The tail is round; number of
toes, five. Three species in Western North America, from California to
Oregon.
_A. lugubris._–The eyes are very large and prominent. The upper jaw shows a
peculiar recess on either side for the reception of the large lower teeth.
The skin is smooth, devoid of parotoid glands, but has a strong gular fold.
The upper parts are dark brown or lead-coloured, with whitish dots on the
sides; under parts white. Total length some 6 inches, about half of which
belongs to the tail. The fingers and toes are very rich in subcutaneous
venous sinuses.
The habits of these creatures are in many respects peculiar. Van
Denburgh[51] says of _A. iecanus_ "that it usually moves quite slowly,
moving one foot at a time, but is capable of motion surprisingly rapid for
a salamander. When moving rapidly, it aids the action of its legs by a
sinuous movement of its whole body and tail. The latter is prehensile.
Several individuals, when held with their heads down, coiled their tails
around my finger, and, when the original hold was released, sustained
themselves for some time by this means alone. One even raised itself high
enough to secure a foothold. This animal's tail is also of use in another
way. When caught, it will often remain motionless, but if touched, will
either run a short distance with great speed, or quickly raising its tail
and striking it forcibly against the surface on which it rests, and
accompanying this with a quick motion of its hind-limbs, will jump from
four to six inches, rising as high as two or three."
Ritter and Miller[52] have made extensive observations on the life-history
of _A. lugubris_. When wishing to pass from the hand to {108}the table, the
creature will frequently execute a well co-ordinated spring and alight on
its feet some distance away, instead of falling over the edge in the
typical salamander-fashion. This species is nocturnal and entirely
terrestrial, and seems to be indifferent even to proximity to water. Rotten
stumps and logs are the habitations preferred, and wherever these occur in
the region about San Francisco Bay, even though at the places remotest from
water, specimens are sure to be found.
The eggs are laid in a hollow under ground, and the female seems to remain
curled around them until they are hatched, which takes place in two or
three weeks. The specimen observed by Ritter and Miller laid 19 eggs. Each
was contained in a gelatinous capsule 6 mm. in diameter, and was firmly
anchored to a clump of earth by a narrow peduncle about 8 mm. long. The
embryos developed very large gills, each being composed of three broad
membranous lobes, the latter being thin and delicate, much expanded, highly
vascular and widely confluent at their bases, so that the gills of each
side really form one three-lobed mass. Their dorsal surfaces are applied to
the inner surface of the egg-capsule. The amount of food-yolk is
considerable. The whole larval life is passed through within the egg.
Before the young is hatched the gills wither and cease to be functional,
and the gill-slits close up. The tail is round, and shows no indication of
a fin at any time during the larval period. Newly hatched individuals
appeared much distressed when put into water, and were quite unable to
swim. They immediately sank to the bottom and remained there until they
were removed. The integumentary sense-organs, so well developed in the
aquatic larvae of Urodeles, are entirely wanting. When hatched the young
creature is about 32 mm. long; its general colour is blackish-grey, finely
sprinkled with bluish-silver. During the second year this garb is changed
to the dusky brown of the adult, and the fine silver speckling is replaced
by much larger and less numerous yellow spots.
Although one of the most terrestrial of Urodeles, this species is lungless,
but the skin remains delicately smooth and moist throughout life. According
to the observers quoted, the pharynx plays an important part in
respiration. From 120 to 180 or even more vibrations are made by the throat
in a minute, and in some cases these movements are grouped into series of
about {109}20 to 25 extremely rapid vibrations, with periods between each
two series.
SUBFAM. 3. AMBLYSTOMATINAE.–Composed of seven closely allied genera, the
distinguishing characters of which are the grouping of the palatal teeth
and the number of the toes, which varies between 4 and 5. The geographical
range of the subfamily extends over the whole of North America and Mexico
and over the whole of Northern Asia, from Kamtchatka and Japan westwards to
the Ural, and southwards into China. The occurrence of one species,
_Amblystoma persimile_, in the mountains of Siam, makes it highly probable
that other species and genera exist in the hitherto unexplored intervening
countries.
Boulenger gives the following synopsis:–
I. The series of palatal teeth converge backwards, forming a V-shaped
figure.
With 5 toes: _Hynobius_, 3 species in Japan.
With 4 toes: _Salamandrella_, 2 species Lake Baikal, Ussuri and Schilka
rivers, and Kamtchatka, p. 109.
II. The series of palatal teeth form an uninterrupted, doubly arched
V-shaped figure.
The 4 fingers and 5 toes are furnished with black, horny claws:
_Onychodactylus japonicus_.
III. The series of palatal teeth form two arches, convex forwards,
separated by a wide interspace.
The two series are short, confined to the space between the choanae.
With 5 toes: _Ranidens sibiricus_, Eastern Siberia and N.E. China.
With 4 toes: _Batrachyperus sinensis_, Moupin in China.
The series are long and converge backwards, 5 toes: _Dicamptodon
ensatus_, California.
IV. The palatal teeth are arranged in a nearly straight, transverse line,
or they form an angle which points slightly forwards; they are not
separated by a wide median space. With 5 toes: _Amblystoma_. Some 16
species in North and Central America, one in Siam, p. 110.
_Salamandrella keyserlingi._–The mode of propagation of this newt-like
species has been observed by Shitkow near Jekaterinburg in the Ural
mountains. The eggs were laid at the end of April and were deposited in
bags, which were attached to a plant, with one end about an inch below the
surface of the water. The bag measured 15 cm. in length and 2 cm. in width
and contained 50 to 60 eggs. The larvae were hatched in 14 days in a sunny
aquarium; in another with a northern {110}aspect the hatching took 23 days.
The larvae were 10 mm. long, and remarkable for the length (1 mm.) of their
balancers.
_Amblystoma opacum._–The general shape is very much like that of the
European Spotted Salamander. The head is short and broad, the snout is
rounded. The eyes are very prominent, with a black pupil and a dark-grey
iris. The neck has a well-marked gular fold. The tail is thick and almost
round. The hind-limbs are considerably larger than the fore-limbs. The
general colour of the shiny, moist skin is a purplish-black with light
grey, transverse, partly confluent bars, giving the creature a pretty
appearance; the under parts are paler, bluish-grey. Total length between 3
and 4 inches, or 9 cm.
This beautiful species inhabits many of the United States east of the Rocky
Mountains, from New Jersey to Florida and Texas. In the perfect state it is
thoroughly terrestrial and easily kept. My specimens prefer the holes of
rotten and moist, moss-covered stumps, or holes beneath stones, which they
leave, at night only, in search of earthworms and insects.
_A. talpoideum_ is closely allied, somewhat stouter and almost uniform
brownish-back. According to Holbrook, "it chooses light soil in which it
will bury itself in a few seconds like a mole, and there continue its
course concealed from view; but its track can often be followed by the
elevation produced on the surface of the soil, similar to that seen in
fields infested by moles."
[Illustration: FIG. 21.–Egg-sac of _Salamandrella schrenki_. × ½. (After
Shitkow.)]
_A. punctatum_ is bluish-black, with a row of roundish yellow spots on each
side of the body and tail and upon the limbs.
E. A. Andrews[53] has made observations upon the breeding of this species.
Near Baltimore the eggs are very abundant in March and even in February, in
small pools in the woods, but the adults are then rarely seen. Even when
small pools, but 4 feet wide and 9 inches deep, were thoroughly raked out
{111}before and after the eggs appeared, no adults were found, so that it
is to be inferred that the laying takes place in the night and that the
adults leave the water every day to conceal themselves under stones. One
female was found moving away from a bunch of eggs early in the morning.
This specimen was kept isolated, and laid many eggs, and as these developed
into normal larvae, the existence of internal fertilisation was proved.
Previously to the laying of the eggs white spermatophores were found in the
small pools, on the dead twigs and leaves covering the bottom.
_A. jeffersonianum._–This very slender and slippery species, reaching a
length of 6 inches, is remarkable for its long fingers and toes, and its
rather compressed tail. The general colour is brown above, dirty whitish
below, generally with numerous, small, light blue and pale brown spots on
the sides of the neck, body, limbs, and tail. There are several
colour-varieties, one of them with white specks. It is a very active and
surprisingly good climber, easily escaping out of high-walled bell-glasses,
hiding in the daytime in dark and moist localities. Its range extends from
Indiana and Virginia to Quebec.
_A. persimile._–This species is remarkable on account of its geographical
distribution. It is the only non-American species, inhabiting the higher
mountains of Siam and Upper Burmah. There is no doubt about its belonging
to the genus _Amblystoma_, although it had originally been described as a
_Plethodon_. It closely resembles _A. jeffersonianum_ in most of its
characters, notably in the arrangement of the palatal teeth, general
proportions, slender toes, and even in the presence of whitish spots, which
are scattered over the sides of its blackish, smooth skin.
_A. tigrinum._–This, the commonest species, is conspicuous for its large,
depressed head, which is as broad as it is long, its width being enhanced
by the unusually large parotoid glands. The mouth is very wide. The large,
prominent eyes are golden, and reticulated with brown. The gular fold is
strong. The limbs are stout, the fingers and toes short. The trunk is
strongly constricted by twelve intercostal grooves. The tail, which is as
long as the rest of the body, is somewhat compressed laterally, but bears
no trace of a fin. The general colour is more or less dark brown or bluish
black, marked with numerous yellow spots and large blotches; the under
surface inclines to {112}grey. The length of the adult male is about half a
foot; the females, as usual being larger, sometimes reach the length of 9
inches. The range is from New York to California and to Central Mexico.
The larva of this species is the famous Axolotl. It is provided with three
pairs of delicate and much-branched external gills, a flat, long tail with
a broad ventral and dorsal fin, the latter extending along the back almost
to the neck. The limbs, although comparatively slender, are fully
developed, and the head is much more pointed than it is in the perfect
form. The larvae usually reach 8 or 9 inches in length; exceptional
specimens have been recorded of one foot in length, and have been described
as _Triton ingens_.
[Illustration: FIG. 22.–Axolotls or larvae of _Amblystoma tigrinum_. × ½.]
These larvae were found by the Spanish conquerors to occur in great numbers
in the lakes near Mexico City, and were called Axolotl by the natives, a
word signifying "play in the water." They were, and are still, eaten,
either roasted or boiled, with vinegar or cayenne pepper.
For many years these creatures were looked upon as a species of the
Perennibranchiata, under the generic name of _Siredon_ (_S. axolotl_, _s.
pisciformis_, _s. mexicanus_, etc.), although Cuvier suspected that they
were but the larvae of an otherwise unknown terrestrial Urodele. The
mystery was not cleared up until the year 1865, when some Axolotls which
had been kept for a year in the Jardin des Plantes at Paris, suddenly began
{113}to pair, and laid eggs which within six months developed into
full-sized Axolotls. This certainly looked as if these creatures were not
larvae, but a true Perennibranchiate species. But to the general surprise
several of these young Axolotls gradually lost their gills, the clefts
closed up, the fins of the back and tail disappeared, the head became
broader, the creatures left the water permanently, and in fact turned into
the already well-known terrestrial _Amblystoma tigrinum_. The other
brothers and sisters of the same brood remained aquatic Axolotls, which
thereby revealed themselves after all as the larval and not as the perfect
stage of this remarkable species.
At the suggestion of Kölliker and Weismann, Frl. Marie von Chauvin[54]
undertook, at the University of Freiburg, long and carefully conducted
experiments, showing (1) that little Axolotls can comparatively easily be
caused to develop further into the perfect _Amblystoma_ if they are induced
to breathe air more frequently than usual; shallow vessels, perhaps also
insufficiently aerated water, will produce the desired result; (2) that the
commencing metamorphosis can again be checked, the shrinking gills then
undergoing fresh development; (3) that they can be forced to remain
Axolotls; (4) that the cutting off of the gills has no influence upon their
possible metamorphosis, the gills being easily and quickly renewed. The
same lady found also that _Amblystoma_, the perfect form, lives in the
water during the pairing time and behaves in the same way as the Axolotls.
The latest observations have been made by Metzdorff.[55] Axolotls, at least
those which are kept in captivity in Europe, are ready for propagation
several times in the year, either in the spring, from April to June, or in
December. The male deposits spermatophores, which in the following night
are taken up by the female into the cloaca. On the following day,
preferably in the afternoon, she grasps a suitable leaf, for instance that
of _Vallisneria_, with the hind-limbs, and presses it against the vent. The
eggs are expelled by strong wriggling movements of the body, and are formed
into three or four packets of six to ten eggs each, so that about thirty
eggs are laid at one sitting. {114}Then she takes a rest before proceeding
again; the whole process, in which the male takes no further interest,
lasting about two days. The most suitable temperature is one of 18-20° C.,
or about 68° F. The water must be well aerated. Sterile eggs turn white on
the second day. The little larvae are hatched in about a fortnight. Eggs
which are kept in a higher temperature, from 22-24° C., develop more
quickly, but the resulting young are smaller; they show already on the
fifth day head, tail, and the beginning of the gills. According to
Bedriaga, they live at first upon Infusoria and _Daphnia_; when they are
20-25 mm. long they eat _Tubifex rivulorum_; later on they take scraped
meat and are liable, when hungry, to nibble off each other's gills, but
these are easily reproduced. When 20-25 cm. long, at the age of about six
months, they are able to breed. The chief point of interest is the fact
that this species of _Amblystoma_ frequently remains throughout life in the
larval state, except that it develops generative organs. The natural causes
of this retention are not completely known. According to Shufeldt, who
observed them under natural conditions near Fort Wingate in New Mexico,
plenty of food, the drying up of the swamps, and the increasing temperature
of the diminishing water, hurries on the metamorphosis, while deeper water
retards it. Weismann[56] suggested that the specimens in the Mexican lakes
which remained Axolotls were prevented from becoming perfect Amblystomas on
account of these lakes, after the disappearance of the surrounding forests,
having receded from their former boundaries, which are now covered with a
saline, uninhabitable crust. This may be an explanation, although Axolotls
do not live in brackish water. But Weismann went farther, and with his
well-known dialectic powers has succeeded in spreading the belief not only
that the Axolotl is a case of reversion to an ancestral stage, but that the
present _Amblystoma_, instead of being the progressive, perfect form, is
likewise a case of reversion. A reversion from a reversion! The whole line
of evolution would then be as follows: _Amblystoma_; its young, owing to
adverse circumstances, revert to the stage of the Perennibranchiate
ancestors of all Urodela; if some of these Axolotls lose their gills and
fins, they revert thereby into the original _Amblystoma_. {115}Surely a
roundabout way of explaining a curious but after all rather simple process
of Neoteny; cf. p. 63.
Observations on the metamorphosis of _Siredon lichenoides_ into _Amblystoma
mavortium_ have been made by Marsh, who also gives figures of the larval
and adult forms.[57]
SUB-FAM. 4. SALAMANDRINAE.–The six genera of this subfamily fall into two
natural groups: I, True Salamanders, with the palatal teeth arranged in a
pair of S-shaped figures, and without a fronto-squamosal arch. II, Tritons,
with the palatal teeth in the shape of a Λ, _i.e._ the right and left
series meet at an angle; the fronto-squamosal arch is present, either bony,
or at least ligamentous. _Triton cristatus_ is, however, exceptional, in
that the two palatal series often do not meet and that the arch is absent.
The number of fingers is universally four, that of the toes is five except
in _Salamandrina_, which has only four.
The geographical distribution of the sub-family, entirely Periarctic, may
be said to be the reverse of that of the Amblystomatinae. Of the
twenty-five species namely, only two are American, four are Eastern
Asiatic, and of the remaining nineteen, two are Algerian, while the rest
live in Europe or in Asia Minor. It is in fact an essentially Palaearctic
group.
The six genera can be distinguished as follows:–
I. The palatal teeth are arranged in two S-shaped curves. True
Salamanders.
Tongue short and thick. _Salamandra_, p. 115.
Tongue long and projectile. _Chioglossa_, p. 121.
II. The palatal teeth are arranged in a Λ shape. True Tritons.
With only four toes. _Salamandrina_, p. 122.
With five toes.
Pterygoids separated from the maxillary and quadrate bones: _Triton_,
p. 122.
Pterygoids touching the maxillae and quadrates. Himalo-Chinese:
_Tylototriton_, p. 132.
Pterygoids united broadly with the maxillae. Chinese: _Pachytriton_,
p. 132.
_Salamandra._–Without fronto-squamosal arch. Five toes. Tail round. Three
species in Europe and Western Asia.
_S. maculosa._–The Spotted or Fire Salamander. General habit stout. Usual
length about 5 to 6 inches; the females are mostly larger than the males;
specimens of more than 8 inches in {116}length are giants. Head as broad as
it is long, snout rounded. Limbs and digits stout and short. The skin is
smooth, shiny and full of pores, with a strong gular fold. The parotoid
glands are large and covered with large pores. A series of distinct
swellings, or cutaneous glands, each with a distinct opening, extends along
either side of the back, and a shorter series along the flanks. The general
colour of the Spotted or Fire-salamander is black, with irregular, large
yellow patches on the back and limbs. These markings vary extremely, so
much so that scarcely two specimens, collected at random, are alike. In
some the yellow patches form two more or less regular bands, in others they
are partly confluent; again the yellow may be preponderant on the back or
much restricted. Occasionally the chrome-yellow is replaced by orange. The
under surface is as a rule bluish grey-black. This combination of shiny
yellow and black is a good instance of warning colours. The creature is
poisonous, cf. p. 38. When left in peace, or handled gently, it is
perfectly harmless, but when treated with violence, or submitted to severe
pain, a milky white fluid exudes from the glands and is, under violent
contractions of the muscular skin and body, sometimes squirted out in fine
jets to the distance of a foot. Burning pain and subsequent inflammation
result if this poison gets into the eye. The same applies to the mucous
lining of the mouth and throat. A few drops of this poison introduced into
the blood or into the stomach of a small animal are sufficient to cause its
death. Cold-blooded animals are as susceptible as warm-blooded creatures.
I once put two American bull-frogs into the same outdoor enclosure with a
large number of salamanders. Next morning the huge frogs were found dead,
each having swallowed a salamander, which they were not acquainted with and
had taken without suspicion.
The Fire-salamander has a wide range, namely the whole of Central,
Southern, and Western Europe with the exception of the British Isles. It
extends southwards into Corsica and Algeria, eastwards through Asia Minor
into Syria. Where it does occur it is rather common, provided the terrain
is mountainous or hilly and covered with vegetation. There it lives under
moss or rotten leaves, in the roots of old trees, in the cracks and clefts
of the ground, of rocks or of ruins of buildings; {117}in default of
anything better under heaps of stones, or in the holes dug by mice or
moles. One chief necessity for its happiness is moisture.
The salamander does not occur everywhere, but is rather local. On certain
kinds of limestone it is rare or absent; granitic terrain and red sandstone
seem to suit it best, for instance the Hartz Mountains, Thuringia, and
Heidelberg are favourite localities. But even there we may spend days and
weeks and never come across a single specimen. We may turn stones, rake up
the moss and leaves, pry into cracks, and we unearth perhaps a few
sorry-looking, listless, dull and dry, half-emaciated creatures. The same
place after a thunderstorm will be literally swarming with sleek, lively
salamanders, in search of earthworms and all kinds of insects, especially
at dusk or during the night. They disappear in the autumn, in October, to
hibernate in the ground, out of the reach of frost, and they reappear again
in April. Later on they congregate at little springs, always at running
water, to reach which they have often to make long migrations. This is the
only time when these thoroughly terrestrial creatures approach water, in
which they easily get drowned.
Although this species is so common its mode of reproduction has been
satisfactorily discovered only quite recently. There are some puzzling
facts which it took a long time to observe correctly and to interpret. The
larvae are born in April, May, or June, while there are no eggs in the
oviducts, but in July these are full of fertilised eggs before copulation
takes place. This seems contradictory. The explanation is as follows. In
July there is an amplexus of the sexes, short, and often on land–a sort of
preliminary exciting performance. Both sexes then descend into the water,
but generally remain on land with the fore part of the body. The male
deposits a spermatophore and the female takes part of this into its cloaca.
In the case of a virgin female the eggs are fertilised in the oviduct and
ripen until the autumn, but the larvae nearly ready for birth remain within
the uterus until the following May, _i.e._ about ten months. The mother
then crawls half into the water, mostly at night, and gives birth to from a
few to fifty young, fifteen being perhaps the average. The young are
surrounded by the egg-membrane, which either bursts before or shortly after
expulsion. This species is consequently viviparous in the proper sense. If
she produces a few young only, say from {118}two to five, these are much
larger and stronger than those of a large litter. Occasionally a few addled
or only partly developed eggs are also expelled.
In the case of old females which have produced offspring before, the whole
process is more complicated. The sperma, taken up in July, remains in the
receptaculum of the cloaca until the May or June following, _i.e._ until
the previous larvae have passed out of the uterus and are born. Then the
spermatozoa ascend to the upper ends of the oviducts, where they meet and
fertilise the new eggs. After these have descended into and filled the
uterus, and are already developing into embryos, copulation takes place
again in July, preparatory for next year's eggs.
The new-born salamanders have three pairs of long external gills, a long
tail furnished with a broad dorsal and ventral fin, and four limbs,
although these are small. The total length is about 25 mm. or 1 inch. The
general colour is blackish with a pretty metallic golden and greenish
lustre. The little creatures are very active, and at once eat living or
dead animal matter. In captivity they are liable to nibble each other's
gills and tails. During the first six or eight weeks they assume a row of
dark spots on the sides; these spots enlarge, and the whole skin becomes
darker. Yellow spots appear next, first above the eyes and on the thighs,
later upon the back; the ground-colour at the same time becomes black,
until at the beginning of the fourth month they look like the parents.
The metamorphosis is very gradual. The tail-fin diminishes first, but the
gills grow until shortly before the little creatures leave the water.
Darkness, cold, and insufficient food retard the metamorphosis, sometimes
until October. It is easy to rear them artificially provided they are well
fed, kept in a light place, and in clean, well aerated water. If prevented
from leaving the latter, for instance when kept in a glass vessel with
vertical walls, or if hindered by a piece of gauze from rising to the
surface and taking in air, they can be kept as larvae well into the winter.
Very young, perfect little salamanders, of from 1 to 2 inches in length,
are excessively rare; even specimens of 3 inches are far from common. They
probably spend the first two or three years of their life in careful
seclusion.
A few adults can be easily kept for many years in shady {119}places
provided with moss, rotten stumps and stones, to afford them suitable moist
and cool hiding-places, and they readily take earthworms, larvae of
beetles, snails, woodlice, etc. But any attempt to keep them in large
numbers ends in failure. They congregate together in clumps, all making for
the same cavity or recess, as if that were the only one in existence (very
likely they are right in so far as that place is probably the best), and
they get rapidly enlarging sores, chiefly on the elbows and knees. These
are soon infested with fungoid growths, and this disease spreads like an
epidemic and soon carries them off.
_S. atra._–The Alpine Salamander differs from the Spotted Salamander by its
uniform black colour and smaller size, which averages between 7 and 5
inches. It is restricted to the Alps of Europe, from Savoy to Carinthia, at
from 2000 to as much as 9000 feet elevation, living with predilection near
waterfalls, the spray of which keeps the neighbourhood moist, or in mossy
walls, in the shade of forests near brooks, or under flat stones on
northern slopes. The most interesting feature of this species is that it
produces only two young at a time. These are nourished at the expense of
the partially developed eggs in the uterus, and they undergo their whole
metamorphosis before they are born. By far the best and most complete
account of this mode of propagation has been given by G. Schwalbe.[58] The
length of the ripe embryos is about 45 mm.; they lie mostly bent up, with
their heads and tails turned towards the head of the mother. The gills are
beautiful, delicate red organs, the first pair being generally directed
forwards and ventralwards, the second upwards, the third backwards; they
are longest when the creature is about 32 mm. long, while there is still
much yolk present. At this stage the gills are so long as to envelop nearly
the whole embryo. There is rarely a second embryo in the same uterus, and
an extra foetus is generally smaller, frequently a monstrosity not fit to
live; it is probable that it is not used as food, but that it is expelled
at parturition. The embryo passes through three stages, (1) still enclosed
within its follicle and living on its own yolk, (2) free within the
vitelline mass which is the product of the other eggs, (3) there is no more
vitelline mass, but the embryo is possessed of gills 10-12 mm. in length,
and is still growing. During the {120}second stage the yolk is directly
swallowed by the mouth. The walls of the maternal uterus are rather red.
The exchange of nutritive fluid takes place through the long external
gills, which thereby function in the same way as the chorionic villi of the
Mammalian egg. Each gill contains a ventral artery and a dorsal vein, each
of which looks like the midrib of a pinnate leaf; there is also a fine
nerve and a weak bundle of striped muscular fibres. Each gill-filament
receives a capillary artery which extends to the epithelium of the tip,
where it turns into a capillary vein. The epithelium of these filaments,
which are full of blood, is ciliated, the resulting current being directed
from the base towards the tip. In older larvae this ciliation becomes
restricted to the tips. The body of the gills is furnished with flat
epithelium, these non-ciliated portions alone are closely appressed to the
uterine wall, and it is here that the exchange of gas takes place between
mother and larva. The nutrition takes place through the gills, as they are
bathed by the yolk-mass.
Schwalbe also explains the whole question of the reduction of the number of
embryos. He says rightly that in _S. maculosa_, which gives birth to many
young, there are in the oviduct many eggs which have only partly developed
into embryos, and these, perhaps from want of room and nourishment,
degenerate into the irregularly shaped whitish-yellow bodies which are
occasionally found packed in between the developing embryos. Consequently
all those eggs had been fertilised near the ovaries. _S. atra_ exhibits a
further stage in so far as most of the eggs, fertilised above in the
oviduct, degenerate, and only two or three become fully developed. These
few embryos live on the degenerating eggs, which together produce the
vitelline material spoken of above. The two full-grown and metamorphosed
embryos, each measuring about 50 mm. in length, are equivalent to the
numerous new-born larvae of _S. maculosa_, especially if the smaller size
of the adult Alpine Salamander is taken into consideration.
Mlle. von Chauvin[59] has experimented with the unborn larvae of this
Salamander. She cut out 23 larvae and put them into water. One of them,
already 43 mm. long, took earthworms on the next day, and the beautiful
long, red gills became pale and shrunk, and on the third day were cast off
close to the {121}body. New gills sprouted out on the same day, first in
the shape of three tiny knobs on either side. After three weeks they had
become round globes, which gradually sprouted out into several branches,
far shorter and more clumsy than the original gills. During the whole time
the larva was lying quietly at the bottom, in the darkest corner, but
showed a good appetite. The fin of the tail disappeared and was supplanted
by a stronger one. In the sixth week the skin was shed in flakes, and this
process took fifteen days. This larva lived in the water for fourteen weeks
and grew to 6 cm. in length! When the new gills gradually shrank, the
compressed and finny tail assumed a round shape, the skin became darker and
shinier, and after the larva had again shed its skin, there appeared the
dark rugose skin of the typical _S. atra_. The gills were reduced to
useless appendages–not cast off–and the creature crawled out of the water.
A fortnight later the gill-clefts were closed. A second larva behaved
similarly, first casting off the feathery gills, substituting a new and
stronger set, which, however, fourteen days after excision from the uterus,
shrank again, and on the nineteenth day the gill-clefts were closed. The
lady also observed that nearly ripe larvae, when cut out, rushed about in
the water and ate, just like the new-born larvae of the Spotted Salamander.
A third species, _S. caucasica_, is found in the Caucasus. It rather
resembles the Spotted Salamander in coloration, but has a larger tail and
lacks the lateral warts. The male is remarkable for the possession of a
soft permanent knob or hook at the top of the root of the tail. This pommel
possibly prevents the slipping off during the amorous amplexus, provided
the sexes then entwine like certain Tritons.
_Chioglossa lusitanica._–The only species of this genus is restricted to
the north-western third of the Iberian peninsula. This graceful,
slenderly-proportioned and beautiful Salamander is apparently very rare and
local, having hitherto been found at a few places, namely, near Coimbra,
Oporto and Coruña. It lives under moss, and runs and climbs with an agility
surprising in a Urodele. The tongue is long, ending in a fork, and is
supported by a median pedicle so that the tip can be quickly protruded to
the distance of more than an inch. The whole length of the animal is about
5 to 6 inches, two-thirds of which belong to {122}the long tail, which is
compressed at the end. The skin is smooth and shiny, with a gular fold and
large parotoids. The general colour is a rich dark brown, with a pair of
broad reddish-golden bands along the back and tail, the bands being
separated by an almost black vertebral line.
The few specimens which I have been lucky enough to observe made little
holes or passages in the moist moss of their cage, peeping out with their
heads in wait for little insects, which they caught with flash-like
quickness. They seem to be crepuscular.
_Salamandrina perspicillata._–This genus, represented by one species, a
native of Liguria and Northern Italy, possibly extending into Dalmatia, is
the only Salamander which has but four toes. The skin is not shiny and
smooth, but is finely granular and dry, forms no gular fold, and is devoid
of parotoid glands. The tail is more than half the length of the animal,
which measures from 3 to 4 inches. The general colour is black-brown with a
broad V-shaped orange-yellow mark extending from eye to eye over the
occiput. A faint irregular yellowish line extends along the middle of the
back and tail. The throat is black, with a diffused white patch in the
middle; the belly is white, with black dots; the anal region, the inner
sides of the legs and the under side of the tail are carmine-red.
This slender and pretty Salamander is diurnal, and feigns death when
discovered. Only the female goes into the water, in March, to glue the eggs
on to submerged rocks or water-plants. The young finish their metamorphosis
by the month of June, and reach full size during the winter, the climate of
their home being sufficiently genial to make hibernation scarcely
necessary.
_Triton_ s. _Molge_.–The tail is strongly compressed and frequently has a
permanent fin. The fronto-squamosal arch is variable, it being either bony
as in the South European, Eastern and American species, or reduced to a
ligament, or lastly absent as in _T. cristatus_. The males of all the
English Newts, of _T. vittatus_ and of _T. marmoratus_, develop a high
cutaneous crest on the back and tail during the breeding season, and this
crest acts not only as a swimming organ and ornament, but also as a sensory
organ.
The whole genus comprises some eighteen species, twelve of which are
European, although some of these extend into Western {123}Asia; _T.
pyrrhogaster_ and _T. sinensis_ are found in N.E. China, the former also in
Japan; _T. poireti_ and _T. hagenmuelleri_ live in Algeria, and only two,
_T. torosus_ and _T. viridescens_, are North American. Some of the species
have a limited range; thus _T. montanus_ is confined to Corsica, _T.
rusconii_ to Sardinia, _T. boscai_ to the north-west of the Iberian
peninsula and _T. asper_ to the Pyrenees.
Newts all prefer moisture without heat. During the pairing season they take
to the water, mostly to stagnant pools, which sometimes implies long
migrations. During this period, which is in some cases rather prolonged,
they become thoroughly aquatic and undergo some important changes. The
tail-fins are much enlarged; in the males of some species a high cutaneous
fold grows out on the back, devoid of muscles, but rich in sense-organs.
The whole skin, instead of being dry, possesses numerous mucous glands and,
what is of more importance, specialised sensory apparatuses which are
arranged chiefly along the lateral lines of the body and part of the tail.
After the breeding season Newts become terrestrial, hiding in cracks,
trees, or in the sandy soil. Some species aestivate during the hot and dry
season. They hibernate either in the ground, or occasionally in ponds. _T.
vulgaris_ is difficult to keep in the water beyond the pairing season,
while this is easily done with _T. alpestris_ and _T. cristatus_; _T.
waltli_ can live in the water for years. The food consists of all kinds of
insects, centipedes, worms, snails, etc., which are searched for chiefly at
night. It is astonishing to see a little Triton getting hold of and
gradually swallowing a wriggling earthworm almost as thick and as long as
itself. When two newts seize the same worm, as these voracious and jealous
creatures often do, each gets hold of one end, and swallowing as much as it
can, twists and rolls round in a direction opposite to that of its rival,
until the worm breaks, or until the jaws of the two newts meet and the
stronger of the two draws it out of the weaker one and swallows the whole
worm. They do not drink, but soak themselves in the water.
The skin is shed periodically, and rather often by the rapidly growing
young; by the adult, during the life in the water, rarely during the
sojourn on dry land. The skin breaks round the mouth; assisted by the
fingers and by contortions of the {124}body, it is then slipped backwards
over the trunk and tail, whereupon the newt seizes the skin with the mouth,
draws the shirt off entirely, and–swallows it. Such freshly shed skins are
very delicate and pretty objects when suspended in water or some preserving
fluid. The shed skin, consisting only of the outermost layer of the
epidermis, is entire, but turned inside out, with fingers and toes
complete, the only holes being those for the mouth, eyes, and vent.
None of the Tritons are viviparous. The eggs, which are glued singly or in
small numbers on to stones or water-plants, are hatched in about a
fortnight, sooner or later according to the species and the prevailing
temperature. The larvae are always provided with three pairs of branched
external gills; the fore-limbs appear much earlier than the hind-limbs.
Most, perhaps all, larvae develop two pairs of thread-like protuberances on
the sides of the upper jaw, by means of which they attach or anchor
themselves on to water-plants shortly after they are hatched. Thus moored
they remain motionless in a slanting position, now and then wriggling their
tails and shifting their place, or sinking to the bottom. The metamorphosis
is finished during the first summer, and the little newts, often partially
transparent, leave the water to hide under stones. Not unfrequently the
metamorphosis is retarded and not finished by the autumn. The larvae of _T.
cristatus_, especially when reared in ponds with abrupt or overhanging
banks, so that they cannot leave the water, retain considerable remnants of
the gills, still more frequently the clefts, although breathing chiefly by
the lungs. Such individuals reach a length of 3 inches, and are larvae so
far as the finny tail and the gills are concerned. They hibernate in this
condition, and in exceptional cases reach sexual maturity;–at least the
females, which develop ripe eggs; the males are not known to produce
spermatozoa.
Much has been written on the amorous games of newts, but it is only
recently that the mode of fecundation has been actually observed. Gasco[60]
placed the newts in glass vessels suspended from the ceiling of his
laboratory. The antics of the enamoured male around the female, rubbing the
latter with its head, or lashing it gently with the tail, and playing
around it in its often beautiful nuptial dress, are meant to excite the
{125}female. The male then at intervals emits spermatophores, which sink to
the bottom, and the female takes them up into its cloaca. For further
information see p. 54.
_Triton cristatus._–The Crested Newt has a slightly tubercular skin with
distinct pores on the head, on the parotoid region and on a line along the
side of the trunk. There is a strong gular fold. The general colour above
is dark or black-brown with an olive tinge, interspersed with darker spots;
the sides of the body bear irregular white spots. The under parts are
yellow, almost always with large black spots. The iris is golden
yellow.–The nuptial dress of the male is very striking. A high, serrated
crest occurs on the head and body; the upper surface of the head is marbled
with black and white; the under parts are orange-yellow with black spots,
and the sides of the tail are adorned with a bluish-white band.–The female,
always devoid of a crest, generally exhibits a yellow line along the middle
of the back.–The average length of fully adult specimens is about 5-6
inches or 13-15 cm.; the females are as usual larger than the males; 144
and 162 mm. for an English male and female respectively are exceptional
records.
[Illustration: FIG. 23.–_Triton cristatus._ 1, Female; 2, male in nuptial
dress. × ⅔.]
Propagation takes place in April. The newly hatched larvae are
yellowish-green, with two black dorsal bands, and with a whitish edge to
the tail-fin. By the middle of July they are about 5 cm. long, and the
white-margined tail now ends in a {126}thread 1 cm. in length. The general
colour above is light olive-brown, dotted with black; the flanks and belly
have a golden shimmer.
The Crested Newt has a wide distribution, extending from England and
Scotland through Central Europe into Transcaucasia; the northern limits are
Scotland and Southern Sweden. Although found in Greece and Lombardy, it
does not occur in the Iberian peninsula nor in the South of France, where
it is represented by the next following species.
_Triton marmoratus._–The Marbled Newt is of the same size as the Crested
Newt. Its ground colour is grass-green above, brown below, with numerous
large and small irregularly shaped marbling patches, spots and dots of
black. The crest of the neck and trunk is entire, not serrated, adorned
with dark vertical bands, and separated from the high dorsal fin of the
tail by a deep indenture or gap. The female has an orange line, slightly
sunk in, instead of the crest. This newt is confined to France and the
Iberian peninsula. In the North of Portugal and in Galicia it is frequently
seen in little streams and ponds during the months of March and April. The
rest of the year it spends on land. In France occur hybrids of this species
and _T. cristatus_. They have been described as _T. blasii_.
_T. alpestris._–The Alpine Newt is easily distinguished by the rich orange
colour of its under parts, which are unspotted, excepting a few dark specks
across the throat, below the gular fold. Specimens with many ventro-lateral
black spots are exceedingly rare. All the upper parts are dark, but vary
individually. The prettiest specimens are dark purplish grey, with black
marblings; others incline more towards brown ground-tones, the blackish
markings then appearing more prominent. The sides are often stippled with
tiny whitish dots. The iris is golden yellow.–The nuptial male has a low,
not serrated crest, which extends uninterruptedly from the nape into the
dorsal fin of the tail. The crest is pale yellow, with black vertical bands
and spots. The ground-colour of the upper parts inclines to blue,
especially on the sides. The lower fin of the tail assumes an irregular
band of bluish-white confluent patches.
This newt is rather small, females rarely exceeding 100 mm. or 4 inches in
length. Its home is chiefly the hilly and mountainous parts of Central
Europe, from Holland to Lombardy, {127}Austria-Hungary, and Greece.
Although it ascends the Alps to between 6000 and 7000 feet, it is also
found in the Netherlands, but not in the North German plain.
_T. vulgaris_ (s. _taeniatus_, s. _punctatus_).–The Common or Spotted Newt
usually reaches 3 inches (7-8 cm.) in length. Boulenger's record-specimen
measured 104 mm. It is characterised by the yellow, partly orange under
surface, which is always spotted with black. The upper parts are
olive-green or brown, inclining to white on the flanks; the black spots of
the back, sides, and especially of the tail, are arranged in more or less
distinct lines, giving a somewhat banded appearance to some females.–The
breeding dress of the male shows a non-serrated, but "festooned" high and
very wavy crest, which extends from the neck without interruption into the
likewise wavy tail-fin. The tail is adorned with a lateral, glittering blue
stripe, interrupted by vertical dark spots. The larvae are marked by a
series of yellow dots, which extend over the lateral line and the tail,
which latter temporarily possesses a terminal filament like that of the
larvae of _T. cristatus_.
The distribution of the Spotted Newt is the same as that of _T. cristatus_,
namely Europe with the exception of the Iberian Peninsula, and Western
Asia.
_T. palmatus_ s. _helveticus_.–This is the smallest of all the European
newts, rarely reaching more than 3 inches in length. It is distinguished by
several specific characters. The tail ends in a thread which is in some
males 10 mm. in length, but is only just indicated in the female. The
breeding male develops a cutaneous fold along each side of the back, and a
low, entire, vertebral crest; the toes are fully webbed. The under parts
are pale yellow, inclining to orange towards the middle of the belly, and
with a few blackish dots. The lower caudal crest has its edge blue in the
male, orange in the female. The general colour of the smooth skin is
olive-brown above, with numerous dark spots, which are arranged in more
longitudinal streaks on the head.
The Webbed Newt is a native of Western middle Europe, ranging from Great
Britain and Northern Spain to Switzerland and Western Germany.
Closely allied to the last species are _T. boscai_ of Spain and Portugal,
_T. italicus_, _T. montadoni_ of Moldavia, and the {128}beautiful _T.
vittatus_ of Asia Minor. From China and Japan are known _T. pyrrhogaster_
and _T. sinensis_.
The North American species are _T. torosus_ and _T. viridescens_. The
former, of Western North America, is one of the largest newts, reaching a
length of more than six inches. The head is much depressed and broad, and
has very prominent parotoid and other glands. The limbs are strong,
especially in the male. The skin of the upper parts is very granular,
uniform dark brown, without a crest. The tail, which is larger than the
head and body, is strongly compressed, with a low dorsal and ventral fin.
The under parts and the lower edge of the tail are uniform yellow or orange
red. The iris is green. A specimen in my keeping spends most of its time in
the cracks of rotten stumps or on the top of moss in the darkest shade. It
lives on earthworms but despises insects. Like most of the other newts it
becomes lively at dusk.
[Illustration: FIG. 24.–_Triton viridescens._ 1, Egg just after deposition,
with the outer membrane opened, × 6; 2, a spermatophore just discharged
showing its gelatinous base with a projecting spike which bears a tuft of
spermatozoa, × 2. (After Jordan.)]
_T. viridescens_ is common throughout the Northern and Eastern parts of the
United States. Large females are about 11 cm. long, the males 1 cm. less.
The general colour above is brown, with a tinge of green; on each side of
the trunk, with a row of bright vermilion spots; the under parts are
orange, studded with small black dots. Half-grown specimens are brownish
red, with the same lateral red spots as the adult. According to Jordan,[61]
this voracious species lives chiefly on the larvae of insects, on small
molluscs such as _Cyclas_ and _Planorbis_, on earthworms and on small
Crustacea. It is eminently aquatic in the adult stage. The eggs are laid
from April to June, the period lasting for one individual four to six
weeks, or even longer. One female laid 108 eggs in all from 20th April to
30th May. After having selected a suitable plant, for instance an
_Anacharis_ or a bunch of _Fontinalis_ leaflets, she bestrides the plant
and gathers in the surrounding shoots with her hind-limbs, {129}pressing
the leaves closely around the cloaca. She next turns on her side, or
occasionally on her back; with fore-limbs outstretched and rigid, with
hind-limbs and leaves completely hiding the cloaca, she remains perfectly
motionless for six to eight minutes. Then she slowly leaves the "nest,"
which now holds an egg well protected by a tangle of shoots glued together
by the gelatinous secretion poured out of the cloaca. Jordan concludes,
from the fact that he never found spermatozoa in the oviducts, that the
eggs are fertilised just before they are expelled, when passing the
receptaculum seminis.
The metamorphosed young pass their life on land under stones and logs as
the so-called red variety, which is merely a stage in the life-history of
the species. It seems to take them several years to reach maturity, and to
become again typically aquatic. Young, red individuals which I have myself
kept, have behaved for more than a year like the young of other newts,
spending their time under moss and bark without going into the water.
The change from the red-spotted stage has been exhaustively studied by
Gage.[62] He remarks that this species is very common near Ithaca, in an
upland forest and along the head-waters of the Susquehannah. The
transformation takes place either in the autumn or in the spring, either
while the newt is still on land, or after entering the water.
Of two which were kept in a jar with moist wood, one was especially
brilliant, but within two weeks it assumed, in the middle of September, the
characteristic coloration of the viridescent form. The two specimens were
in the jar until the following July, when they were placed where they could
enter the water. This they did with great readiness, and they remained
submerged for a considerable time at first. The time under water increased
in length, until within two or three days the pharyngeal respiration under
water was fully established. On the other hand, viridescent specimens never
reassume the red garb when kept out of the water.
Red specimens entering the water in the spring, changed into the greenish
form within a few weeks, and established the pharyngeal respiration, losing
the ciliated oral epithelium. Branchiate larvae and the adult aquatic forms
have non-ciliated {130}epithelium, and the cilia are re-established when a
green specimen is forced again to live on land. Ciliation always exists in
the red stage, and in the green stage before the newt has taken to the
water. The cilia sweep towards the stomach.
The three following South European species belong to the _Euproctus_ group,
so called on account of the mostly conical, backward directed, and vividly
coloured vent.
_T. asper_ s. _pyrenaeus_.–The Pyrenean newt has hitherto been found only
in the Pyrenees, for instance in Lac Bleu and Lac d'Oncet, which latter
lies about 7000 feet above the level of the sea. According to Bedriaga,[63]
it prefers lakes which are supplied during the whole summer with water from
glaciers. It is very sluggish, only moving to breathe and when in search of
food, which consists of worms and insects. The general colour is greenish
brown, dark above; the under side of the head and body are bright orange
red in the female, yellow in the male; dark spots separate this bright
colour from the flanks. The tail has a narrow ventral stripe of bright red
and yellow. The cloaca of the female is bright red, that of the male dull
grey. The total length amounts to about 4 inches or 10 cm.
The pairing time is the end of June, or later in cold seasons. The male
gets hold of the female by forming a noose with its tail round her; it lies
underneath, the cloacae being pressed together so that the spermatozoa can
be taken in directly. The larvae have large yellow-green spots on the back
and sides, and a bright red ventral tail-fin; when metamorphosed the
greenish spots become more confluent on the back, producing a broad spinal
band. Larvae which live in deep water are dark, while those in sunny places
are light-coloured and spotted with yellow.
_T. montanus_ in Corsica and _T. rusconii_ in Sardinia are allied forms,
but the males are distinguished by a spur-like process or dilatation at the
end of the fibula.
_T. waltli_, the Iberian Newt, is olive-brown above, yellowish with
blackish markings below. The tail has a yellow or orange ventral line.
There is no crest. A remarkable peculiarity of this species (which it
shares only with _Tylototriton andersoni_ of the Loo-Choo Islands) is its
ribs, which are very long, sharply pointed, and frequently perforate the
skin. Before {131}perforation the point of the rib lies in a lymphatic
space. This surprising feature has by many authorities been considered as
abnormal or pathological. Certainly young, and even many adult, individuals
are found in which the skin is not perforated, but when these are handled
the wriggling motions of this strong newt force the points of the ribs
through the skin, and they remain sticking out to the extent of several
millimetres. The wounds heal up, the skin forming a neatly finished-off
hole through which the spike projects, not as a formidable, but as a
sufficiently awkward, protective weapon.
[Illustration: FIG. 25.–_Triton waltli._ Spanish Newt, adult and larvae. ×
⅔.]
Large females reach a length of 10 inches. The larvae metamorphose, as a
rule, when they are between 2 and 3 inches long, but those which have been
bred in tanks often reach double this length. These newts are frequent
inhabitants of the rain-water cisterns common in the South of Portugal and
Spain, into which they tumble without ever being able to get out again.
This species spends most of its time in the water, {132}preferring ponds,
among the vegetation of which they can be watched lying motionless, with
their limbs hanging down and with the head close to the surface; but they
are lively during the night. When their ponds dry up they leave them,
crawling into the most unexpected places, to aestivate under rocks, or even
in the walls of old buildings, where they are found by accident only. The
range extends from Central Spain and Portugal into Morocco.
_Tylototriton verrucosus_ lives in the Eastern Himalayas and in the
mountains of Yunnan. The skin is tubercular, with large parotoids; above
uniform black-brown, pale below; the tail has a ventral yellow or orange
line. Total length about 6 inches. _T. andersoni_ of the Loo-Choo Islands
is remarkable for the pointed ribs which perforate the skin.
_Pachytriton brevipes_, discovered in Kiansi, Southern China, has a smooth
skin, olive-brown above, with many black dots; the under parts are
yellowish, dotted with black. Total length about 7 inches.
FAM. 3. PROTEIDAE.–The three pairs of fringed external gills persist
throughout life. Both fore- and hind-limbs are present. The eyes are devoid
of lids. The maxillaries are absent. Teeth are present on the
premaxillaries, on the vomers, and on the mandible. The vertebrae are
amphicoelous.
This family consists of only three genera, with one species in each.
_Necturus maculatus_ s. _Menobranchus lateralis_.–The eyes are functional,
being covered by the thin transparent skin. The limbs, although short, are
well developed, and have four fingers and four toes. The whole animal,
which reaches the length of one foot, is quite smooth and slimy, brown with
irregular dark, blackish spots and patches, which frequently form a dark
lateral band extending from the mouth to the tail. The latter, which
measures about one-third of the whole length, is strongly compressed,
carries a thick dorsal and ventral fin, and is rounded off at the end. The
skin of the throat forms a strongly-marked transverse fold. The thick
stalks of the gills are brown, while the numerous and delicate fringes are
dark red in life; beneath and behind them are two gill-clefts. _N.
maculatus_ is found in the eastern half of the United States, chiefly the
eastern part of the basin of the Mississippi and the Canadian lakes.
{133}These creatures are rather dull; they remain mostly at the bottom of
the water, more or less concealed in the weeds or between rocks during the
daytime. Mine, which are kept in a roomy, light-coloured tank, lie
motionless, with their gills spread out transversely. Every now and then
the gills contract suddenly and become pale, whereupon they are filled
again with blood. Very rarely they rise to the surface, but tiny
air-bubbles are let out more frequently, especially when the animals are
disturbed. Then the gills collapse, are laid flat against the neck, and the
creature darts about with quick, eel-like motions. At night they leave
their hiding-places, swim about or creep along the ground with slow,
undulating movements, the limbs being scarcely used, in search of food,
which in their wild state consists of rather large Crustacea, small fishes,
worms, insects and frogs. They are most voracious, and absolutely
indifferent to cold. The spawning takes place in the months of April and
May.
_Proteus anguinus._–The fore- and hind-limbs are fully developed, but
possess only three fingers and two toes. The eyes are completely hidden
beneath the opaque skin. This peculiar creature is restricted to the
subterranean waters of Carniola, Carinthia, and Dalmatia. The vast caves of
Adelsberg not far from Trieste are especially celebrated for the occurrence
of the "Olm," the German name of this animal. The river Poik, a moderate
mountain-stream, but a large, fierce torrent during the rainy season,
disappears into the limestone-hills, and rushes through enormous
stalactite-grottoes, most of which have been only partially explored, until
several miles farther on it reappears on the surface. There, deep down
below the surface, in absolute darkness, in an almost constant temperature
of about 50° F. is the home of _Proteus_.
Their total length is scarcely one foot. The whole body is white,
occasionally suffused with a slight fleshy, rosy tinge, while the three
pairs of gill-bunches are carmine-red. They are easily kept in captivity,
and live for many years, provided three conditions are strictly adhered to,
viz. fresh and clean water, an equable low temperature of about 50° F. =
10° C. and darkness. The question of food is not so very important, since
specimens are known to have existed for years, although they refused to
take any nourishment. How far darkness is an {134}absolute necessity is not
known. Anyhow, the white skin is almost as susceptible to light as is a
photographic plate. If light is not absolutely excluded the white skin
becomes in time cloudy, with grey patches, and if kept exposed to stronger
light, the whole animal turns ultimately jet-black. Mr. Bles has succeeded
in producing several totally black specimens, having kept them for several
months in a white basin under ordinary conditions of light. No experiments
have yet been made to find out if the black pigment deposited is lost again
in darkness. Those which are kept in a tank in an absolutely dark cellar of
the Cambridge Museum, with permanent water-supply, are doing very well.
When approached with a candle they become restless or remain partly hidden
in all sorts of seemingly most uncomfortable attitudes, squeezed in between
the sharp-edged tiles and drain-pipes with which their lodgings are
furnished. But the introduction of a wriggling worm, a little crustacean or
other live bait draws them from their hiding-places, and, guided by the
motions of the prey in the water, possibly also by the sense of smell, they
snap it up and devour it.
[Illustration: FIG. 26.–_Proteus anguinus._ × ⅔. Front view of the mouth in
the left upper corner.]
If the water is not sufficiently well aerated, they rise to the surface,
emit a bubble of air, and take a new supply into their lungs. As a rule
they remain motionless under water, but the gills contract spasmodically
and become paler, whereupon they fill again with blood and darken; the
contrast between the pure white body and the carmine-red feathery gills is
very beautiful.
Until recently the mode of propagation was quite unknown. Several
_Proteus_, kept by E. Zeller, laid, in the middle of April, {135}a number
of eggs which were then fastened singly on to the under side of projecting
stones in the water. The pale yellow yolk measured 4 mm. in diameter and
was surrounded by a cover of 1 mm. in thickness, besides an outer
gelatinous mantle, so that the whole egg measured about 11 mm. The larvae
were hatched after 90 days; they were 22 mm. long, and already much like
the adult, except that the fin was not restricted to the tail, but extended
over the last quarter of the trunk, and that their eyes were still visible.
The fore-limbs were already typical in shape, but the hind-limbs were still
toe-less little stumps.[64]
_Typhlomolge rathbuni._–It is of the greatest interest that a subterranean
Perennibranchiate newt, in many respects closely resembling _Proteus_, has
recently been discovered in Texas. There can be no doubt that similar
conditions of life have produced these two forms from _Necturus_- and
_Spelerpes_-like ancestors,[65] one in Europe, the other in North America,
absolutely independently of each other. The limbs of _Typhlomolge_ are long
and very slender, the four fingers and five toes are thin, free and
pointed. The head is large, the mouth square. The eyes are completely
hidden and the whole animal is colourless and white. The tail is furnished
with a dorsal and a ventral fin. The very deep gular fold is nothing but
the pair of united but large opercular flaps. The three pairs of gills are
remarkable for their blade-like stalks, while the gill-lamellae proper are
short and restricted to the tapering ends. Total length about 75 mm., of
which the head measures 15, the tail 32 mm.
This peculiar creature inhabits subterranean caves in Texas, to judge from
the fact that all the specimens hitherto known have come up with the water
of an artesian well 188 feet deep, near San Marcos. According to
Blackford,[66] "the legs are used for locomotion and the animals creep
along the bottom of the aquarium with a peculiar movement, swinging the
legs in irregular circles at each step. They climb easily over the rocks
piled in the aquarium, and hide in the crevices between them. All efforts
to induce them to eat have been futile, as has also been the case with
blind cave-fish in captivity, and they are {136}either capable of long
fasts or live on infusoria in the water." It seems more reasonable to
suppose that these newts live upon Crustacea, four kinds of which, all new
to science, also came up with the water.
FAM. 4. SIRENIDAE.–The three pairs of fringed external gills persist
throughout life. The body is eel-like. Hind-limbs are altogether absent,
while the fore-limbs are short and have three or four fingers. The
maxillary bones are absent. With the exception of small teeth on the vomer
the mouth is toothless, but the jaws are furnished with horny sheaths. The
eyes are devoid of lids, but shine through the skin.
[Illustration: FIG. 27.–_Siren lacertina._ × ½.]
The Sirenidae are the most degraded members of the Urodela and are
represented by two closely-allied genera, each with one species, in the
south-eastern parts of the United States. Their most interesting feature,
which bears upon the question of neoteny, is their retrograde metamorphosis
as described by Cope.[67] The gills atrophy in the young and are
subsequently redeveloped. Cope therefrom concludes rightly that the
ultimate or persistent gills of _Siren_ are signs of maturity and not a
larval character. In young specimens of _Siren_ of 5 to 6 inches in length
the gills are functionless; in one of 3 inches they were found to be
entirely vestigial and "subepidermal," _i.e._ covered by a common dermal
investment. Unfortunately really young larvae are still unknown. Old Sirens
can live without gills, as has been shown by aquarium-specimens. In the
adult _Pseudobranchus_ all the gills are normally covered up by an
investment of the skin so as to be quite without function and movability.
_Siren lacertina_, the "mud-eel," is distinguished by the {137}possession
of three pairs of gill-clefts and by its four fingers. It reaches a length
of 70 cm., or about 2½ feet, of which about one-third is taken up by the
tail, which is strongly compressed and finned. The skin is smooth, mostly
blackish, lighter below, sometimes with whitish specks all over the body.
This creature is frequently found in ditches and ponds, where it burrows in
the mud. When swimming the limbs are folded back. They are said sometimes
to leave the water and to crawl about on the moist ground.
_Pseudobranchus striatus_ has only one pair of gill-clefts and only three
fingers. The slightly granular skin is dusky brown above, with a broad
yellow band on either side and with a paler, narrower stripe below. Total
length about 7 inches.
{138}CHAPTER VI
LISSAMPHIBIA (_CONTINUED_)–ANURA
ORDER III. ANURA OR TAILLESS AMPHIBIA.
The recent tailless Amphibia, or Frogs and Toads in the widest sense,
contain such a great number of species (about 900), with such a diversity
of characters, that it is necessary, if only for the sake of mere
convenience, to group them into a considerable number of families and
sub-families. The characters available for this purpose are few.
1. The possession of a tongue characterises the PHANEROGLOSSA, the
absence of a tongue the AGLOSSA.
2. The character of the shoulder-girdle.–Overlapping of the two halves of
the shoulder-girdle on the ventral side characterises the ARCIFERA, while
in the FIRMISTERNIA the two ventral halves meet in the middle line and
form a firm, median bar. See, for details, p. 24.
3. The shape of the transverse processes or diapophyses of the sacral
vertebra which carries the iliac or hip-bones. These processes are either
_dilated_ or _cylindrical_.
4. The presence or absence of teeth in the upper and lower jaws. This is
indicated by a formula in which 0 means absence of teeth; max. means
presence of teeth in the upper jaw; mand. means presence of teeth in the
lower jaw.
5. The terminal joints or phalanges of the fingers and toes are sometimes
_claw-shaped_. See p. 26.
6. The shape of the centra of the vertebrae.–_Opisthocoelous_, if the
posterior end is cup-shaped or concave, _procoelous_ if the anterior end
is concave and the posterior is convex. See p. 19.
By means of these characters we can arrange the Anura in the following
key:–
I. Aglossa. Sacral diapophyses dilated. } AGLOSSA, p. 143. {139}
Vertebrae opisthocoelous, with ribs. }
II. Phaneroglossa.
_A_. Arcifera.
_a_. Sacral diapophyses dilated.
α. Terminal phalanges not claw-shaped.
Opisthocoelous, with ribs,
max./0 } DISCOGLOSSIDAE, p. 152.
Procoelous, without ribs, 0/0 } BUFONIDAE, p. 166.
Precocious, or opisthocoelous,}
without ribs, max./0 } PELOBATIDAE, p. 160.
β. Terminal phalanges claw-shaped–HYLIDAE
{ max./mand. _Amphignathodontinae_,
{ p. 188.
{ max./0 _Hylinae_, p. 189.
_b_. Sacral diapophyses cylindrical–CYSTIGNATHIDAE
{ max./mand. _Hemiphractinae_,
{ p. 210.
{ max./0 _Cystignathinae_, p. 211.
{ 0/0 _Dendrophryniscinae_, p. 227.
_B_. Firmisternia.
_a_. Sacral diapophyses dilated–ENGYSTOMATIDAE
{ max./0 _Dyscophinae_, p. 235.
{ 0/mand. _Genyophryninae_, p. 236.
{ 0/0 _Engystomatinae_, p. 225.
_b_. Sacral diapophyses cylindrical–RANIDAE
{ max./mand. _Ceratobatrachinae_,
{ p. 237.
{ max./0 _Raninae_, p. 238.
{ 0/0 _Dendrobatinae_, p. 272.
Concerning the evolution of the classification of the Anura, it is
interesting to follow the changes of the value attached to the various
anatomical characters by systematists. At first the presence or absence of
teeth and of adhesive discs on the fingers and toes were considered to be
of prime importance for the division of the Phaneroglossa.
Duméril et Bibron, 1841. "Erpétologie générale."
I. PHRYNAGLOSSES = Aglossa of Wagler: _Pipa_ and _Xenopus_.
II. PHANÉROGLOSSES. 1. With teeth. _a_. Without discs: Raniformes.
_b_. With discs: Hylaeformes.
2. Toothless. Bufoniformes.
Stannius, 1856 (see p. 8), separated the Engystomatidae as "Systomata," and
used the presence or absence of the "manubrium sterni" (omosternum) as a
character of distinction between his Bufoninae and Raninae.
{140}Günther, 1858, "Catalogue of the Batrachia Salientia." No progress was
made by his scheme, which relied upon the tongue and digits.
Aglossa with _Myobatrachus_.
Opisthoglossa. _a_. Oxydactyla. _b_. Platydactyla.
Proteroglossa: Rhinophrynidae.
Cope, 1864. "On the limits and relations of the Raniformes."[68] He
introduces the shoulder-girdle and the sacral diapophyses, and drops the
discs as too adaptive and misleading. He distinguishes between RANIFORMES
and ARCIFERI.
Cope, 1865. "Sketch of the primary groups of the Batrachia Salientia."[69]
Aglossa.
Bufoniformia (Bufonidae).
Arcifera (Discoglossidae, Scaphiopodidae, and Hylidae).
Raniformia.
In 1867 Cope separates the genus _Hemisus_ as Gastrechmia on account of its
peculiar pectoral arch.[70]
In 1875, "Check-list of North American Batrachia and Reptilia," Cope
elaborates his system:
Class Batrachia. Order Anura.
1. Raniformia.
2. Firmisternia. [Dendrobatinae and Engystomatidae.]
3. Gastrechmia: _Hemisus_.
4. Bufoniformia. [Bufonidae.]
5. Aglossa. _Pipa._
6. Odontaglossa. _Xenopus._
7. Arcifera. [Cystignathidae, Hylidae, Pelobatidae and Discoglossidae.]
Cope consequently considered the characters of the pectoral arch as
equivalent to those of the dentition.
Boulenger, 1882, "Catalogue of the Batrachia Gradientia s. Ecaudata,"
recognises that the pectoral arch is of greater systematic value than the
dentition. The latter is used, together with the shape of the sacral
diapophyses, for the separation into families.
I. Phaneroglossa. _A_. Firmisternia. { 1. Ranidae.
{ 2. Dendrobatidae.
{ 3. Engystomatidae.
{ 4. Dyscophidae.
_B_. Arcifera. { 5. Cystignathidae.
{ 6. Dendrophryniscidae.
{ 7. Bufonidae.
{ 8. Hylidae.
{ 9. Pelobatidae.
{ 10. Discoglossidae.
{ 11. Hemiphractidae.
{ 12. Amphignathodontidae.
II. Aglossa. { 13. Dactylethridae.
{ 14. Pipidae.
{141}This emendation of the Arcifera and Firmisternia was accepted by Cope
in his synopsis of the families of Vertebrata (_Amer. Natural._ xxiii.,
1890), except that he still retained his suborder Gastrechmia.
Since the publication of Boulenger's great work a number of forms have been
discovered which, from the characters of their dentition, have necessitated
the establishment of certain new families, namely, Ceratobatrachidae and
Genyophrynidae; and Boulenger was the first to recognise that the taxonomic
value of the mere presence or absence of teeth in the jaws had been
overestimated. I therefore propose using it as a character distinctive of
the sub-families only, thereby reducing the number of families, relying
first (leaving the Aglossa aside) upon the firmisternal or arciferous
condition of the pectoral arch, secondly upon the dilated or cylindrical
shape of the sacral diapophyses, thirdly upon the dentition. Blindly
consistent application of these principles would reduce the Phaneroglossa
to four families only, namely Ranidae, Engystomatidae, Cystignathidae and a
fourth family comprising all the Arcifera with dilated sacral diapophyses.
This would obviously be wrong. We have therefore to resort to other
additional characters or rather peculiarities. The opisthocoelous character
of the vertebrae and the possession of distinct ribs, together with the
disc-shaped tongue, separate the Discoglossidae and justify their retention
as a family. The Hylidae are marked off by the claw-shaped terminal
phalanges, but the remaining forms, comprising the Bufonidae and
Pelobatidae, cannot be separated except by their dentition, and I plead
guilty of inconsistency in retaining them as separate families.
After all, our classification may not represent the natural system, and it
may be nothing but a convenient key.
When we have eliminated the characters of the vertebrae, the dentition, the
claw-shaped phalanges and the adhesive discs, it may well be asked what
characters remain. The firmisternal is a further, higher modification of
the older, more primitive arciferous condition. The difference between the
dilated and cylindrical shape of the sacral diapophyses is in not a few
cases very slight, and there are various, most suggestive exceptions. The
presence or absence, size and shape of the omosternum and metasternum are
of very limited taxonomic value, not always applicable to all {142}the
members of the same family. The fact is, that the Anura are a very recent
and a most adaptive, plastic group. The earliest known fossils are scarcely
older than the Middle Eocene.
Almost every one of the greater families has produced terrestrial,
arboreal, aquatic, and burrowing forms. Their habits have modified, and are
still shaping their various organs, first of course those by which the
animals come first and most directly into contact with their surroundings
(_e.g._ adhesive discs, dentition, general shape of the body, length of
limbs, wartiness of the skin, tympanic disc). These are the so-called
adaptive characters, sometimes decried as merely physiological; as if
habits, use, and requirements did not likewise influence and ultimately
model every other organ (_e.g._ tympanic cavity, Eustachian tubes,
vertebrae, ribs, coccyx, pectoral arch, etc.). There are true Toads,
Bufonidae, which are as smooth, wartless, slender-bodied and long-legged as
the most typical of "Frogs"; true Ranidae, like _Rhacophorus_, which by
their green colour, large adhesive discs and arboreal habits may well put
many of the Hylidæ to shame. _Ceratohyla_ has developed the claw-shaped
terminal phalanges which are otherwise typical of, and peculiar to, the
Hylidae, but this genus reveals itself by various details as a close
relation of the other Hemiphractinae; and these fall in with the
Cystignathidae on the strength of their cylindrical, not dilated, sacral
diapophyses.
In sketching the phylogenetic tree of the families of the Anura we have to
proceed with great caution.
There is not much doubt about the Aglossa. They have retained some of the
most primitive characters, but have by now been so much modified and
specialised that they are to be looked upon as an early side-branch.
Among the Phaneroglossa the Discoglossidae are with certainty the oldest,
but are now scarce in genera and species, and much specialised. The
Pelobatidae connect them with the Bufonidae. The Cystignathidae form a
rather ill-defined assembly which points downwards to the Pelobatidae,
upwards to the Hylidae. There is no divergence of opinion about the Ranidae
being the highest of all the Anura, and amongst them the Raninae the most
typical, the Dendrobatinae the most specialised. If we assume that
moderately dilated sacral diapophyses represent a more primitive stage than
cylindrical processes, we shall {143}naturally look to the Engystomatidae
as the connecting link between the Ranidae and the Arcifera, through
Bufonoid creatures still with teeth in both jaws. If, on the other hand, we
take the dilatation to be a further development from more or less
cylindrical processes, then the Ranidae can be considered as having sprung
from Cystignathoid creatures, which have consolidated their pectoral arch
into the firmisternal condition; and in this case the Firmisternia would
not be a natural group, the Engystomatidae pointing, to the Bufonoid stock.
This would, to a great extent, mean a reversion to Cope's idea.
SUB-ORDER 1. AGLOSSA.–The two diagnostic peculiarities of the few members
of this group are: first, the absence of a tongue; secondly, the union of
the Eustachian tubes into one median pharyngeal opening in the posterior
portion of the palate.
[Illustration: FIG. 28.–Map showing distribution of Aglossa. _Hymenochirus_
to be added in Equatorial Africa.]
The pharyngeal opening and the tubes themselves are wide, the tympanic
cavities are present, but the tympanic discs are not distinct from the rest
of the skin. The fronto-parietal bones are fused into one mass, a rare
feature in the Anura. The nasals are large. _Pipa_ and _Hymenochirus_ have
no teeth, _Xenopus_ has teeth on the upper jaw. The vertebrae are
opisthocoelous and typically epichordal in their development; the second,
third, and fourth carry long ribs, which in old specimens fuse with the
supporting diapophyses. The sacral diapophyses are enormously dilated, and
the sacrum is fused with the os coccygeum. The serial number of the sacral
vertebrae exhibits a most interesting gradation. In _Xenopus_ the ilium is
carried by the diapophyses of the 9th, in _Pipa_ the 9th and 8th, in
_Hymenochirus_ the 7th and 6th. In these cases the two diapophyses of each
side are fused together into a single broad blade, and their original
duplicity is indicated only by the {144}holes for the spinal nerves.
_Hymenochirus_ has consequently only 5 presacral vertebrae, the vertebral
column being shortened to the greatest extent known amongst Vertebrata. For
further information see p. 22. The ilia are much broadened vertically, and
are firmly attached to the sacrum. The shoulder-girdle is sometimes
described as of the arciferous type, but this is quite unjustifiable. The
epicoracoid cartilages do not overlap each other, but meet, and partly fuse
in the middle line. The three genera exhibit some differences. In _Pipa_
and _Hymenochirus_ the bony portions of the coracoids are much expanded
dorsally, and there is a considerable amount of epicoracoid cartilage, that
of the precoracoid bars extending backwards as a broad-based and blunt
omosternum. _Xenopus_ is devoid of an omosternum, and the configuration of
the whole apparatus is more slender. The metasternum of _Xenopus_ and
_Hymenochirus_ broadens out laterally. _Hymenochirus_ greatly resembles
_Breviceps_, a genus of Engystomatinae, in the relative position and size
of the various parts of the shoulder-girdle and sternum.
The tibio-fibula of _Hymenochirus_ has a wing-like expansion of thin bone
on each side, forming a deep groove on the outer aspect. The astragalus and
calcaneum are united by a similar bony expansion with wing-like
projections.
The lungs are remarkable for the prominent development of trabecular
projections and niches, so that their free lumen is much restricted; they
have thereby reached a much higher stage than in any other Amphibia or even
many Autosauri. The persistence of an arteria sacralis s. caudalis, a
vessel absolutely absent in the adult _Rana_, is a primitive feature, and
the same applies to the presence of a true first spinal or suboccipital
nerve.
The skin of the back and belly is supplied by two great branches from the
arteria anonyma, one arising proximally, the other distally from the
subclavian; herewith is correlated the almost complete absence of the
arteria cutanea magna, which as a branch of the ductus pulmo-cutaneus plays
such a prominent rôle in the other Anura. Only in _Pipa_, but not in
_Xenopus_, is the great cutaneous vein represented by a very small branch.
Both these genera possess a much more complicated "diaphragm" than the
other Anura, chiefly owing to a special muscle which arises {145}from the
anterior end of the ilia and spreads out fan-like to the oesophagus and to
the bases of the lungs.[71] This diaphragmatic arrangement is correlated
with the great development of the lungs, and is not a primitive but an
advanced feature. It is reasonable to suppose that this has caused the
reduction of the usual arteria pulmo-cutanea, and that the other two
cutaneous arteries have been developed secondarily. The Aglossa are
generally considered as the lowest Anura, and only Cope looked upon _Pipa_
and _Xenopus_ as two convergent terminal branches. Beddard came to the
conclusion that both are closely related to each other, chiefly on account
of their peculiar diaphragmatic arrangement. The whole question has entered
upon a new stage since the recent discovery of _Hymenochirus_, which is in
many ways intermediate between the two other genera. Moreover, the
mid-Tertiary _Palaeobatrachus_ of Europe is undoubtedly related to them,
and we conclude now that all these four genera belong to one group with a
distribution formerly much wider than Africa and part of South America. But
this does not necessarily mean that the Aglossa are in all respects the
most primitive group of living Anura. On the contrary, they possess few
decidedly primitive characters, namely, the long typical ribs, the presence
of the first spinal nerve, the unimportant persistence of the arteria
sacralis, and lastly, the possession in the tadpoles of a right and left
opercular "spiracle." The absence of the tongue cannot possibly be an
archaic feature, considering its universal presence in all the other
Amphibia, including the Apoda, and the suggestive circumstance that this
organ is least developed in the entirely aquatic members of the Urodela. In
fact, thoroughly aquatic creatures, which seize and swallow their prey
under water, require no elaborate tongue; and since we know that the Anura
must owe their typical formation to terrestrial life, it follows that those
which have again taken to the water and are tongueless, have lost this
organ. As I have shown elsewhere,[72] the epichordal development of the
vertebrae is likewise a secondary feature, far from primitive; and the
tendency of the shortening of the vertebral column, which has reached its
extreme in _Hymenochirus_, points to the same conclusion. The apparatus of
the shoulder-girdle and sternum is in the last transitional stage from the
former arciferous to the typically consolidated firmisternal {146}type. In
fact there is little left which is primitive, but much that is very
specialised and highly developed in the Aglossa, mostly in adaptation to
their absolutely aquatic life, to which they must however have taken very
early. They are in a position somewhat analogous to the Ratitae among
Birds, which are likewise an old group, although many of their most
striking features have been acquired secondarily.
_Xenopus_ s. _Dactylethra_. The upper jaw is furnished with teeth. The ilia
are attached to the ninth vertebra. The pupil is round. The terminal
phalanges are pointed. The fingers are free, the toes broadly webbed, and
the first three are covered with sharply pointed, horny, black-brown nails,
a feature which is alluded to by the alternative generic names. A cutaneous
tentacle projects from below the eye and naturally invites comparison with
the tentacle of the Apoda and of Urodela. The skin is smooth, rich in
mucous glands, besides certain tube-like apparatuses, possibly sensory,
which are scattered over the body, especially on the head, and form a
conspicuous series of white dots along the dorso-lateral line, from the eye
to the vent. The general colour of the upper parts is olive brown, mottled
darker, while the under parts are whitish. The female has three cutaneous
flaps closing the vent. The male develops black nuptial brushes along the
inner side of the fingers. There are several species, all African
(Ethiopian).
_X. laevis_, ranging from the Cape to Abyssinia, is distinguished by the
absence of a metatarsal spur. The tentacle is very short. Size about 3
inches. _X. muelleri_ of Zanzibar and Benguella, is smaller. The tentacle
is conspicuous, as long as the diameter of the eye. The inner metatarsal
tubercle carries a sharp claw. _X. calcaratus_ of tropical West Africa is
only 2 inches long, and has strong metatarsal claws, short tentacles and
very minute eyes.
The habits and oviposition of the "Clawed Toad" have been described by
Leslie.[73] The Boers call it "Plathander," _i.e._ flat hand. Entirely
aquatic, it rests floating in the water, with the nostrils exposed, and
leaves the water only if it has to change the locality on account of
drought or scarcity of food. The pairing takes place, at least at Port
Elizabeth, in the early spring, _i.e._ in the month of August. The only
sound which is emitted is heard during this time, a very slight and dull
tick-tick, audible at only a few feet distance. The male grasps the female
by the loins; the eggs are extruded singly, measuring only 1.5 mm. in
diameter, but swell to double that size. They are attached singly to stones
or water-plants.
{147}[Illustration: FIG. 29.–_Xenopus laevis._ Clawed Toad, adult and
larvae, × ⅔.]
{148}Latterly these creatures have frequently been brought over to England.
They stand confinement very well, even in a little aquarium with sufficient
water-weeds to keep the water fresh; and they do not require special heat.
They greedily snap up worms, strips of liver, or meat, and poke the food in
with their hands. A few kept by Boulenger in a glass jar have lived for the
last eleven years in the ordinary temperature of a room in London.
Curiously enough they are often in amorous embrace, regardless of the
season, but they have never shown any signs of spawning.
Some of those in the Zoological Gardens in London laid eggs on Saturday the
27th of May, and on the morning of the following Monday the larvae were
already hatched. They have been described by Beddard.[74] The larvae are
provided with an unpaired circular, ventral sucker. The tentacles begin to
sprout out on the sixth day after hatching, at first not in connexion with
the cranial cartilage, but soon a cartilaginous rod runs into the tentacle
from the ethmoid "just above the joint with the under jaw.". Boulenger has
most reasonably compared these organs with the "balancers" of _Triton_ and
_Amitystoma_ (cf. p. 46 for the possible homologies of the balancers). The
tentacles soon reach a great length and give the tadpole a curious
appearance. In tadpoles of _X. calcaratus_, 65 mm. long, the tentacles are
30 mm. long, and are inserted just at the angle of the mouth. By the time
that these tadpoles show their fore-limbs, the feelers are reduced to 4 mm.
in length, and their relative position has been shifted to a little above
the angle of the gape, and whilst the latter gradually extends further and
further back, the feelers come to lie, or rather remain, below and a little
in front of the eyes.
The tadpoles have no traces of horny teeth. External gills project as low
conical or lamellar processes from the first three branchial arches, but
so-called internal gills are not developed.
Amongst a number of Clawed Toads imported in the spring one female became
swollen with eggs, but as they did not show signs of wanting to breed, a
pair was put into the tropical tank {149}in the Cambridge Botanic Gardens,
a transfer which had the desired effect. Eggs were laid, and more during
the following nights; they hatched out within thirty hours. The whole brood
was lost, before any of them were older than a few days, since they were
attacked, beyond the possibility of a cure, by a _Saprolegnia_ or some
similar pest.
_Hymenochirus_, represented by one species, _H. boettgeri_, has been
discovered in the Ituri, German East Africa, and in the French Congo, and
has no doubt a much wider distribution. It is scarcely 1½ inch long, and is
easily recognised by the toothless mouth, the half-webbed fingers (hence
the generic name), the incompletely webbed toes, the third of which is
longer than the fourth, and the absence of sensory muciferous canals in the
skin. The three inner toes are, as in _Xenopus_, furnished with small black
claws. The skin is rough, beset with small granular tubercles. The general
colour above and below is olive-brown. The vent is, as in _Xenopus_,
produced into a spout or semi-canal, but is devoid of dorsal flaps of skin.
_Pipa._–This Neotropical member of the Aglossa is quite toothless, but the
jaws of the adult have horny substitutes. The only species is _P.
americana_, the famous Surinam Toad, chiefly known from the Guianas, but
undoubtedly extending much further, having recently been reported from the
neighbourhood of Pará.
The general shape of this creature is very peculiar. The head is much
depressed and triangular; the eyes are very small; the skin forms several
short, irregularly-shaped flaps and tentacles on the upper lips and in
front of the eye, and at the angle of the mouth. The tympanum is invisible.
The pupil is round. The fingers are very slender and free, ending in
star-shaped tips; the toes are broadly webbed. The whole skin is covered
with small tubercles and is dark brown above, while the under parts of the
very flat and depressed body are whitish, sometimes with a dark brown
stripe along the middle line. In the female the skin of the back forms
growths for the reception of the eggs, and in these the young undergo their
whole metamorphosis.
{150}[Illustration: FIG. 30.–_Pipa americana._ Surinam Toad. × ⅔.]
{151}The most characteristic feature of the skin,[75] which has exactly the
same structure in both sexes, is the papillae, which are spread over the
whole surface, except on the webs of the toes, on the cornea and on the
star-shaped points of the fingers. Each papilla carries a little horny
spike, and a poison-gland frequently opens near its base. Larger
poison-glands exist on the dorsal and ventral side in four rows, and
smaller glands open upon the sides of the body, but there are no parotoid
complexes. Slime-glands occur all over the surface. The epidermis consists
of the usual layers, namely the Malpighian, the stratum corneum, and the
part which is shed periodically. The latter is completely horny, appearing
to be structureless like a cuticle, but it is in reality composed of
polygonal cells with flattened nuclei; each little spike is one modified
horny cell. The whole outermost layer contains black-brown pigment. The
upper portion of the cutis is devoid of pigment, then follows a layer of
clusters of ramified dark pigment-cells, and lastly the rest of the cutis.
Each of the four fingers ends in a four-armed star, the tips of which again
carry four or five sensory papillae. The cartilage of the terminal
phalanges is correspondingly star-shaped.
According to Klinckowstroem these toads, which are entirely aquatic, are
easily collected at the end of the long dry period, when they are all
confined to the half-dried-up pools. But they do not spawn there. This
happens after the rains have inundated the forest, and then it is very
difficult to get the females with eggs on their backs. Each of the eggs,
when once they have been glued on to the back, sinks into an invagination
of the skin. The initial stages are probably the same as those caused by
the eggs on the belly of _Rhacophorus reticulatus_ (see p. 248). Later,
each egg is quite concealed in a cavity with a lid. These cavities are
simply pouches of the skin, and are not formed by enlarged glands as has
been suggested by some anatomists. Each cavity consists of the epidermal
pouch and the lid. How the latter is produced is not known. According to
the authors quoted above, the lid looks like a shiny or sticky layer which
has hardened into horn-like consistency. It lies exactly like a lid upon
the rim of the pouch itself, and is certainly not in structural or organic
continuity with the epidermis. Most probably it is produced by the remnant
of the egg-shell itself, which, after the larva is hatched, is cast up to
and remains on the top of the cup.
{152}Bartlett[76] has described the spawning of specimens in the Zoological
Gardens in London.
"About the 28th of April 1896 the males became very lively, and were
constantly heard uttering their most remarkable metallic, ticking
call-notes. On examination we then observed two of the males clasping
tightly round the lower part of the bodies of the females, the hind parts
of the males extending beyond those of the females. On the following
morning the keeper arrived in time to witness the mode in which the eggs
were deposited. The oviduct of the female protruded from her body more than
an inch in length, and the bladder-like protrusion being retroverted,
passed under the belly of the male on to her own back. The male appeared to
press tightly upon this protruded bag and to squeeze it from side to side,
apparently pressing the eggs forward one by one on to the back of the
female. By this movement the eggs were spread with nearly uniform
smoothness over the whole surface of the back of the female to which they
became firmly adherent. On the operation being completed, the males left
their places on the females, and the enlarged and projected oviduct
gradually disappeared from one of the females. In the other specimen, the
oviduct appears not to have discharged the whole of the eggs."
Boulenger, who examined this second specimen, which died, confirmed this
egg-bound condition. He remarks further: "The ovipositor formed by the
cloaca (not by the prolapsed uterus), was still protruding and much
inflamed. It may be deduced from the observation made by the keeper, that
fecundation must take place before the extrusion of the eggs, and it is
probable that the ovipositor serves in the first instance to collect the
spermatozoa which would penetrate into the oviducts, the eggs being laid in
the impregnated condition, as in tailed Batrachians."
SUB-ORDER 2. PHANEROGLOSSA–FAM. 1. DISCOGLOSSIDAE.–The tongue has the shape
of a round disc, adherent by nearly the whole of its base, and it cannot be
protruded. The vertebrae are opisthocoelous, and in the aquatic genera are
of the most exaggerated epichordal type; the diapophyses of the second to
the fourth vertebrae carry short, free ribs, and those of the sacral
vertebra are dilated. The metasternum behind is forked. The {153}upper jaw
and the vomers are provided with teeth. The males have no vocal sac. The
tadpoles are distinguished by having the opercular spiracle placed in the
middle of the thoracic region (see general anatomical part, p. 44).
The few members of this family have a peculiar distribution. _Liopelma_ is
confined to New Zealand, where it is the solitary representative of the
Amphibia. _Ascaphus_ is found in North America. The other genera,
_Discoglossus_, _Bombinator_, and _Alytes_, are typical of the Palaearctic
sub-region, and are, with the exception of _Bombinator_, confined to the
Western Provinces (cf. Map, Fig. 32, on p. 161).
_Discoglossus._–The tympanum is frequently more or less concealed by the
skin. The pupil is round or triangular. The omosternum is small. The
vertebrae are of the epichordal type.
_D. pictus_, the only species, has a smooth and shiny skin, provided with
numerous small mucous glands. The palms of the hands are provided with
three tubercles, of which the innermost is the largest, and is carried by
the vestige of the thumb. The coloration of this species is very variable.
The ground-colour of the upper parts is a rich olive brown with darker,
light-edged patches, which are either separate or confluent in various
ways, forming broad, longitudinal bands, or a few larger asymmetrical
patches, separated in some individuals by a broad and conspicuous light
brown or yellowish vertebral stripe. An irregular reddish band frequently
extends from the eyes backwards along the sides. The under parts are mostly
yellowish white. This variability is purely individual, the most
differently marked and variously coloured specimens being found in the same
locality and even amongst the members of one and the same brood. The male
develops various nuptial excrescences, consisting of minute, dark, horny
spines, notably on the inner palmar pad, on the inner side of the first and
second finger, on the chin and throat, and smaller and more scattered
spicules on the belly and legs.
This pretty and extremely active little creature, which measures between 2
and 3 inches in length, is confined to the south-western corner of the
Palaearctic sub-region, being found in Algiers and Morocco, Sicily,
Sardinia, Corsica, and the southern and western parts of the Iberian
Peninsula. Curiously {154}enough it is absent in the Balearic Isles. Rather
aquatic in its habits, frequenting pools and streams, it is also often
found on land.
The male has a feeble voice, which sounds like "ha-a, ha-a-a," or
"wa-wa-wa," uttered in rapid succession. The pairing season lasts a long
time, in Algeria from January to October, but a much shorter time in the
north of Portugal, where it extends over the spring and summer months.
Boulenger has made extensive observations on many specimens kept in
captivity. The embrace, which never lasts long, is lumbar. The eggs are
small, 1 to 1.5 mm. in diameter, dark brown above and greyish below, each
surrounded by a gelatinous capsule of 3-7 mm. in diameter. The eggs are
laid singly, and a set amounts to from 300 to 1000, the whole mass sinking
to the bottom of the pool. Each female lays several times during the
season. The eggs are developed very rapidly, the larvae escaping sometimes
after thirty-six hours, but usually from the second to the fourth day. The
external gills are lost on the seventh day, when the tadpoles are 11 mm.
long; the hind-limbs appear on the tenth, and after four weeks the tadpoles
reach their greatest length, namely from 25-30 mm. The fore-limbs appear on
the thirtieth day, and a few days later the most precocious specimens leave
the water and hop about. Others, however, of the same brood took from two
to three months in metamorphosing.
This species lives on insects and worms, and can swallow its prey under
water.
_Bombinator._–The tympanum is absent and the Eustachian tubes are very
minute. The pupil is triangular. The omosternum is absent. The vertebrae
are absolutely epichordal. The fingers are free, the toes are webbed. The
upper parts are uniformly dark, and are covered with small porous warts.
The general shape of the head and body is depressed or flattened downwards.
The habits are eminently aquatic. This genus consists of three species, two
of which are European, the third Chinese.
_B. igneus._–The under parts are conspicuously coloured bluish black with
large irregular red or orange-red patches; the upper parts are more or less
dark grey or olive black. The iris is golden, speckled with brown. The male
has a pair of internal vocal sacs by which the throat can be inflated;
nuptial excrescences are developed on the inner side of the fore-arm and
the {155}first two fingers. Total length from 1½ to 2 inches, the males
being generally smaller than the females. This "Fire-bellied toad," the
"Unke" of the Germans, is essentially a native of lakes, ponds, and other
standing waters of the plains.
It ranges through the whole of North Germany, Bohemia, and Hungary into
Russia, eastwards as far as the Volga. The latter river, the Danube, and
the Weser form, roughly speaking, its boundaries; northwards it extends
into Denmark and the southern extremity of Sweden.
[Illustration: FIG. 31.–_Bombinator igneus._ × 1. Fire-bellied Toad. Two of
them in "warning" attitude.]
_B. pachypus._–The under parts are yellow instead of red. The male is
devoid of vocal sacs, but has nuptial excrescences on the under surface of
most of the toes, in addition to those on the fore-arm and fingers. The
"Yellow-bellied Toad" is the representative of the red-bellied species in
Southern and Western Europe, preferring, although not exclusively, the
hilly and mountainous districts. It ranges from France and Belgium through
South-Western Germany, continental Italy, and the whole of Austria and
Turkey in Europe. Where both species meet, for instance in the hilly
districts between the Weser and the Rhine, in Thuringia and in Austria, the
predilection of the yellow-bellied {156}species for the hills, and that of
the other for the plains, is well marked.
While _B. igneus_ prefers standing waters with plenty of vegetation, _B.
pachypus_ is often found in the smallest occasional puddles produced by
recent rain, for instance in the ruts of roads. Both species have otherwise
much in common. They are essentially aquatic. They hang in the water, with
their legs extended, nose and eyes just above the surface, and bask or lie
in wait for passing insects, the fire-bellied kind preferring to conceal
itself in the vegetation of the margins of ponds. During the pairing
season, in Germany in the month of May, they are very lively and perform
peculiar concerts, one male beginning with a slowly repeated note like
"hoonk, hoonk," or "ooh, ooh," in which all the other males soon join, so
that, when there are many, an almost continuous music is produced. This
sound is not at all loud, a little mournful and very deceptive. It appears
to be a long way off, certainly at the other end of the pond, until by
careful watching you see the little creature almost at your very feet. But
on the slightest disturbance the performance ceases, they dive below and
hide at the bottom. The yellow-bellied kind, when surprised in a shallow
puddle, skims over the mud, disturbs it, and allows it to settle upon its
flat body, so that nothing but the little glittering eyes will betray its
concealment. When these toads are surprised on land, or roughly touched,
they assume a most peculiar attitude, as shown in Fig. 31. The head is
partly thrown back, the limbs are turned upwards with their under surfaces
outwards, and the whole body is curved up so that as much as possible of
the bright yellow or red markings of the under parts is exposed to view.
The creature remains in this strained position until all danger seems
passed. In reality this is an exhibition of warning colours, to show the
enemy what a dangerous animal he would have to deal with. The secretion of
the skin is very poisonous, and the fire-toads are thereby well protected.
I know of no creature which will eat or even harm them. I have kept numbers
in a large vivarium, together with various snakes, water-tortoises, and
crocodiles, but for years the little fire-bellies remained unmolested,
although they shared a pond in which no other frog or newt could live
without being eaten. Hungry water-tortoises stalk them under water, touch
the intended prey with the nose in order to {157}get the right scent, and
then they withdraw from the _Bombinator_, which has remained motionless,
well knowing that quick movements, or a show of escape, would most likely
induce the tortoise to a hasty snap, with consequences to be regretted by
both.
After they have been handled frequently, they do not readily perform, but
simply lie still, or hop away. Miss Durham experienced considerable
difficulty in inducing her tame specimens to assume and to keep up the
correct warning attitude. The statement that they "turn over on the back"
is a fable, graphically fixed in various illustrated works.
It has been said that these two species are diurnal and thoroughly aquatic.
They are certainly active in the daytime, sing in full sunshine, and spend
most of their time in the water, but they display much more liveliness
towards the evening and during the night, especially when there is a moon.
My fire-toads live by no means always in the water, but conceal themselves
in the daytime under stones, while they are regularly all astir at night in
search of worms and all kinds of small insects.
The spawning takes place several times during the spring and summer. The
amplexus is lumbar, and the eggs are extruded singly. They sink to the
bottom, or are attached to water-plants. The oviposition takes a long time,
perhaps the whole night, and several dozen eggs, not hundreds as in the
allied genera, make a set. The egg, with its swollen gelatinous capsule, is
large for so small a creature, namely 7-8 mm. in diameter. The embryos
escape after a week, and the tadpoles reach two inches in total length.
Those of _B. igneus_ have a triangular mouth, but in _B. pachypus_ this is
elliptical, as in _Alytes_ and _Discoglossus_. Metamorphosis is completed
in the same autumn; the little toad is then about 15 mm. long, and differs
from the adult by the absence of the conspicuous coloration of the under
parts. In reasonable conformity herewith it does not take up the warning
attitude. The colour appears gradually during the second year, but full
growth is generally not reached until the third year. They do not hibernate
in the water, but hide on land out of the reach of frost.
_Alytes._–The tympanum is distinct, the pupil vertical, the omosternum is
absent. The only two species live in South-Western Europe. The male
attaches the eggs to its hind limbs, and nurses them until they are
hatched.
{158}_A. obstetricans_, the "Midwife-toad," has the general appearance of a
smooth toad. The upper parts are rather smooth, sometimes almost shiny, in
spite of the numerous more or less prominent warts, of which those of the
lateral lines, and those above the ear, are generally most marked. The
colour of the upper parts varies a great deal according to the prevalence
of greenish and reddish spots upon the grey or brown ground-colour. The red
is sometimes, especially in the breeding males, rather conspicuous on the
parotoid region and on the upper sides of the body. The under parts are
whitish grey. The iris is pale golden, with black veins. The male has no
vocal sac, and is as a rule smaller than the female, the latter reaching a
length of two inches.
This species occurs in the whole of the Iberian Peninsula and in France,
extending into Switzerland and beyond the Rhine valley into Thuringia.
Altitude above the sea does not seem to have any influence upon its range,
which reaches from sea-level to the tops of subalpine mountains. I have
found great quantities of its tadpoles in Portugal on the Serra d'Estrella,
nearly 6000 feet high, and they are recorded from 6500 feet in the
Pyrenees. They seem to be ubiquitous in Spain and Portugal, not that they
are often found or seen, but they are heard everywhere; besides, tadpoles
are sure to be in the clear cold lakes on the tops of the mountain-ranges,
in the dirty puddles caused by the village fountains, and in the sun-heated
swampy ditches on the roadside with scarcely enough water to hold the
wriggling mass. Wherever there is water within easy reach, on the lonely
mountains, in fertile valleys, in the gardens of the busy towns, you hear
during the whole night, from March to August, the double call-note of the
male, sounding like a little bell; but to see the performer is quite a
different matter. He sits in front of his hole, dug out by himself or
appropriated from a mouse, in a crack of the bottom of a wall, under
stones, or in a similar place into which he withdraws for the day.
The pairing and the peculiar mode of taking care of the eggs by the male,
which habit has given it the specific name _obstetricans_, the midwife,
have been most carefully observed by A. de l'Isle du Dréneuf, near Nantes.
A condensed account has been given by Boulenger. Several males collect
around a female on land, not in the water, and the successful one grasps
{159}her round the waist. For nearly half an hour the male lubricates the
cloacal region of the female by more than one thousand strokes of his toes,
whereupon the female extends the hind-limbs, forming with the bent
hind-limbs of the male a receptacle for the eggs, which are then expelled
with a sudden noise. The eggs are yellow and large, up to 5 mm. in
diameter, and are fastened together in two rosary-like strings, several
dozen making one set. During the expulsion of the eggs the male shifts its
body forwards, clasps his fore-limbs round the female's head, and
fecundates the eggs. After a rest he pushes first one hind-limb and then
the other through the convoluted mass of eggs, which then have the
appearance of being wound round the hind-limbs in a figure of 8. Then the
sexes separate and the male withdraws with its precious load into its hole,
which it, however, leaves during the following nights, in search of food,
taking this opportunity to moisten the eggs in the dew, occasionally even
immersing them in the water. After at least three weeks, when the larvae
are nearly ready, he betakes himself to the nearest water, and the larvae
burst the thereby softened gelatinous cover of the eggs. Not infrequently
the same male ventures upon a second pairing, and adds another load to the
one which already hampers its movements. The eggs being large, owing to the
great amount of yellow food-yolk, the embryos are enabled to be hatched in
a more advanced stage than in most other Anura. The larva develops only one
pair of external gills within the egg. These appear first in the shape of
oval bags upon the third branchial arch, which sprout out secondary
branches, soon in their turn to be resorbed and replaced by the so-called
internal gills before hatching.
Fischer-Sigwart[77] gives the following account of the growth of this
species. The male took to the water, with its load of twenty to thirty
eggs, on the 6th of June. The larvae escaped out at once, 16-17 mm. long,
the body measuring 5 mm. On the 14th they had reached 32 mm. in length,
whereupon they grew very slowly, although they were well fed, in a
temperature of about 50° F. This same brood did not metamorphose until May
of the next year. The growth took place as follows:–The hind-limbs appeared
on the 8th of September, when the tadpoles were 50 mm. long; by the middle
of the next May they {160}had reached their greatest length, 76 mm., the
hind-limbs being 18 mm. long, whilst the fore-legs were just indicated. On
the 21st of May the hind-limbs were 27 mm. long, and the whole creature was
practically metamorphosed, except for the tail. The latter was resorbed on
the 13th of July, and the little toads, 25 mm. in length, were actually
smaller, certainly far less bulky and heavy, than the tadpoles, which had
required one year and a quarter for their metamorphosis.
The early broods probably finish their development by the autumn of the
same year, but those which are born later, in July and August, certainly
hibernate in the water. I have found very small tadpoles, scarcely 15 mm.
long, on the Cantabrian mountains as late as the end of September, and
rather large ones in the spring at the time of first pairing; the fact that
this takes place during the whole summer explains the occurrence of
tadpoles in all stages of development almost the whole year round.
_A. cisternasi_ has only two palmar tubercles, the middle or third one of
_A. obstetricans_ being absent; the outer finger is short and thick.
Instead of a very long and wide fronto-parietal fontanelle, the
fronto-parietal bones diverge only in front so that there are two
fontanelles, a small one in the parietal and a large triangular one in the
frontal region. The limbs are relatively shorter and stouter in conformity
with the habits of this species, which prefers to burrow in sandy
localities. Otherwise it leads the same kind of life as _A. obstetricans_,
and the male carries the eggs. It has hitherto been found in Central Spain
and in the middle provinces of Portugal.
_Liopelma_ is intermediate between _Alytes_ and _Bombinator_, agreeing with
the latter, in conformity with its essentially aquatic life, in the absence
of a tympanum, while the Eustachian tubes are entirely suppressed. The
tongue is disc-shaped, but is slightly free behind. The pupil is
triangular. The male is devoid of a vocal sac. _L. hochstetteri_ is the
sole representative of the Amphibia in New Zealand, where it is apparently
rare. The upper parts are covered with smooth tubercles, and are dark brown
with blackish spots; the under parts are whitish. Total length only 1½
inch.
FAM. 2. PELOBATIDAE.–The upper jaw and, as a rule, the vomers are provided
with teeth. The tongue is oval, slightly {161}nicked, and free behind, so
that it can be thrown out, except in _Asterophrys turpicola_ of New Guinea,
which has a large but entirely adherent tongue. The vertebrae are
procoelous, except in _Asterophrys_ and the Malay genus _Megalophrys_,
where they are opisthocoelous. The sacral diapophyses are strongly dilated.
The omosternum is small and cartilaginous. The metasternum has a bony
style, and ends in a cartilaginous, rounded or heart-shaped disc, but in
_Scaphiopus_ it forms an entirely cartilaginous plate. The tympanic disc is
mostly hidden or indistinct, and is quite absent in _Pelobates_. The
Eustachian tubes are very small in _Pelobates_, and exceedingly minute in
_Scaphiopus stagnalis_ of New Mexico. The pupil is vertical. This family
contains seven genera with about twenty species, with a rather scattered
distribution.
[Illustration: FIG. 32.–Map showing distribution of Cystignathidae,
Discoglossidae, and Pelobatidae.]
_A._ Toes extensively webbed, sacrum and coccyx confluent.
_a._ Metasternum a cartilaginous plate. America ..........
_Scaphiopus_, p. 164.
_b._ Metasternum with a bony style. Europe .......... _Pelobates_,
p. 162.
_B._ Toes nearly free. Metasternum with a bony style.
_a._ Vertebrae procoelous.
α. Sacral vertebra articulating by one condyle with the coccyx.