|
NEWT (a corrupted See also: family Salatnandridae which constitute the genus Molge, formerly known as See also: Triton
.
But the name Triton, applied to these Batrachians by N
.
Laurenti (1768), has already been used by See also: Linnaeus (Systema Naturae) for parts of the See also: barnacle (Lepas anatifera)
.
B
.
Merem (182o) proposed to substitute for it the name Molge, said to be derived from the Gr
.
MOX.ytis or Marts, " slow," in allusion to the movements of these animals on See also: land
.
The similar name Molch designates these Batrachians in See also: German
.
The newts are very closely related to the true Salamanders, Salamandra, from which they differ principally in the shape of the tail, which is compressed, in relation to their aquatic habits during a considerable See also: part of the active See also: period
.
Their aquatic progression is effected principally by means of the tail, and during the See also: act of swimming the legs are turned backwards and folded against the See also: body and tail, so as to admit of the smallest possible
degree of resistance
.
A very marked sexual dimorphism prevails in most See also: species of this genus, the See also: males being more brilliantly coloured than the See also: females and provided with a dorsal crest which attains its greatest development during the breeding season, lasting through the spring and the early summer
.
Later in the season the males more or less completely lose their crests and other nuptial ornaments, and the two sexes are more alike; they then retire on
land, concealing themselves under stones, logs of See also: wood, or 1n holes in See also: damp See also: earth, but leaving their retreat at See also: night or in wet weather to See also: search for earth-See also: worms and slugs which constitute their See also: principal See also: food
.
In the See also: water they are very destructive of tadpoles, See also: insect larvae and crustaceans
.
A remarkable feature of the newts, which they share with the other tailed Batrachians and the larvae of the frogs and toads, is theSee also: great facility with which they regenerate, lost parts, such as the tail, limbs, and even the See also: eye, a faculty which has given rise to a great variety of experiments, from the days of See also: Charles '
See also: Bonnet and See also: Spallanzani to those of the See also: present school of Entwickelungsmechanik
.
Extraordinary as it may appear, considering the abundance of these creatures and the See also: attention they have received from naturalists, it was only in 188o that their mode of fecundation was correctly ascertained, from observation of the See also: common newt by the See also: Italian zoologist F
.
Gasco
.
The amorous See also: games of the newts, so graphically represented by M
.
Rusconi, had been repeatedly described, and See also: Abbe Spallanzani, as early as 1766, had ascertained the impregnation to be See also: internal
.
The then current belief that the water served as a vehicle to convey the spermatozoa to the See also: female See also: organs had received a See also: blow on Karl Theodor von Siebold's See also: discovery of a receptaculum seminis in the female, but no satisfactory explanation had been given of the manner in which the. spermatozoa reach these pouches
.
This mystery
.
Gasco succeeded in elucidating in, his masterly paper published in 188o, which has since been supplemented by his own investigations on the See also: axolotl, and those of E
.
See also: Zeller, E
.
O
.
See also: Jordan and others on the See also: European and See also: American newts
.
All who have kept newts in an See also: aquarium have witnessed the curious antics of the male placing himself before the female and rapidly vibrating his folded tail, or bending his body in a semicircle, as if to prevent her from passing ahead of him
.
The male then emits, at See also: short intervals, in front of the female, several conical or See also: bell-shaped spermatophores (a gelatinous secretion from the See also: cloaca), adhering to the ground and crowned by a spherical mass of spermatozoa, which the female afterwards gathers in the lips of her cloaca either by See also: mere application or by holding the spermatophore between her See also: hind legs and pressing the, mass of spermatozoa into the cloaca, whence they ultimately find their way into the See also: lower part of the oviducts, where the eggs are fecundated as they descend
.
The larvae are provided with three pairs of long, fringed, plume-like See also: external gills, which are not lost until the very last stages of the See also: metamorphosis, and, in exceptional cases are even retained through-out See also: life, the newt breeding in the branchiate condition, as often happens in the axolotl
.
The fore limbs are See also: developed before the hind limbs
.
The genus Molge has a wide distribution, extending over See also: Europe; See also: north-west See also: Africa, See also: south-western See also: Asia, eastern temperate Asia (See also: China and See also: Japan) and North See also: America as far south as See also: southern California and the Rio Grande del Norte
.
Twenty species are distinguished
.
The See also: British species are the crested newt (M. cristata), the common newt (M. vulgaris) and the palmated newt (M. palmata)
.
The first is the largest, and See also: measures 4 to 6 in
.
The skin is more or less rugose, with granular warts, a strong See also: fold extends across the throat, and the male is provided with a very high dentate dorsal crest which is interrupted over the sacral region; the upper parts are dark, with more or less distinct black spots; the sides are speckled with See also: white, and the lower parts are yellow or orange, spotted or marbled with black; a silvery stripe adorns the
See also: side of the tail in the male
.
The common and the palmated newts are smaller, 2'-,-, to 4 in. in length, and have a smooth skin
.
The dorsal crest of the male is high and festooned in the former, low and straight-edged in the latter; during the breeding season the feet of the common newt are lobate like a See also: grebe's, whilst they are webbed like a See also: duck's in the palmated newt, which is further distinguished in having the tail truncate and terminating in a filament
.
It is a remarkable fact that, although related so closely and occur-ring so frequently together in pools of small extent, the common add palmated newts are not known ever to produce hybrids, whilst the crested newt, when coexisting (in some parts of See also: France) with a south-western ally, the' beautiful Molge marmorata, to which it is by no means more nearly akin than are the two above-named species to each other, regularly gives rise to the See also: form known as M. blasii, which has been proved to be a See also: cross. between M. cristata and M. marmorata
.
Principal references: G
.
A . Boulenger, See also: Catalogue of See also: Batrachia Gradientia s
.
Caudata (1882) ; J. de Bedriaga, Lurchfauna Europas, II
.
Urodela (1897); F
.
Gasco, Sviluppo del Tritone alpestre," See also: Ann
.
Mies
.
See also: Geneva, xvi
.
(188o) ; E
.
Zeller, " Befruchtung bei den Urodelea," Z
.
Wiss
.
Zool. xlix
.
(1890) and li
.
(1891); M . Rusconi, Amours' See also: des Salamandres aquatiques (1821) ; W
.
Wolterstorff, " Ober Tritonblasii," Zool
.
Jahrb., Syst., xix. p
.
647 (1904)
.
|
|
|
[back] NEWSPAPERS |
[next] NEWTON |
There are no comments yet for this article.
Do not copy, download, transfer, or otherwise replicate the site content in whole or in part.
Links to articles and home page are encouraged.