United States or Heard Island and McDonald Islands ? Vote for the TOP Country of the Week !
The boy corporals and Brenda Arnold climbed eminences, looked through clefts in precipices into the sublime depths of the great cañon, stood on the edge of craters of extinct volcanoes, penetrated the mysterious caverns of the cliff-dwellers, fished for trout in a mountain lake, caught axolotl in a tank at the foot of San Francisco Mountain, shot turkeys, grouse, and antelope, and enjoyed the march as only healthy youngsters can.
Experimentally, thyroid has been used to transform one into the other. Thus the occasional change of a Mexican axolotl, a purely aquatic newt, breathing through gills, into the amblystoma, a terrestrial salamander, with spotted skin, breathing by means of lungs, has long been known. Feeding the axolotl on thyroid gland produces the metamorphosis very quickly, even if the axolotl is kept in water.
In the reptile house at the London Zoological Gardens full-grown examples of the common black axolotl and the pretty white variety are exhibited. Some are nearly three inches long. Alongside are shown several examples of the amblystoma stage, produced in one of the laboratories of Oxford University and at the gardens by thyroid feeding.
In the few small lakes near the city of Mexico where it occurs it has never been known to undergo metamorphosis but is aquatic throughout its life and breeds in that condition. Yet in captivity by reducing the quantity of water in which it is placed the young Axolotl can be forced to breathe air, and then it undergoes complete metamorphosis to the abranchiate condition.
There are frogs, like the tree-frog of Martinique, and others in regions where water is scarce, which never pass through the tadpole stage; or, to be quite accurate, they lose the gills and tail in the egg, as higher land-animals do. On the other hand, there is a modern Amphibian, the axolotl of Mexico, which retains the gills throughout life, and never lives on land. Dr.
There is nothing very surprising in the fact that excess in the case of the Axolotl causes the occurrence of the metamorphosis which had already in numerous experiments been produced by forcing the animals to breathe air.
It is the axolotl, which partakes of the form of a fish, and abounds in many of the lakes in Mexico. It is much esteemed as an article of food by the inhabitants of the neighbourhood. We cannot speak of Mexico without having our minds drawn to the time of the Aztec monarchy, when sumptuous palaces, enormous temples, fortresses, and other public edifices covered the face of the country.
Again, in Spelerpes rubra, where almost vertically ascending articular processes above are repeated by almost vertically descending articular processes below. Also in the axolotl, where there are douple pits, placed side by side, not only superiorly but at the same time inferiorly. This kind of homology is also explained by Mr.
Occasionally the latter unite, so as to form a jagged line along the back. Among the batrachians found in Mexico is the curious axolotl, which frequents the great lake on which the chief city is built, as well as numerous other lakes, some at a considerable elevation above the ocean. It is between eight and ten inches long, of rather a dark greyish-brown colour, thickly covered with black spots.
Moreover, there is no evidence that there is any deficiency of thyroid in the Axolotl. The secretion of the thyroid gland is necessary for the normal growth and development of all Vertebrates, and we are only beginning to understand the effects of defect or excess of this secretion.
Word Of The Day