United States or Paraguay ? Vote for the TOP Country of the Week !
In the Devonian fishes the vertebrae, as well as the other parts of the skeleton, have not ossified, or changed to bone, but remain in their primitive cartilaginous condition. THE TAIL FIN IS VERTEBRATED. The backbone runs through the fin and is fringed above and below with its vertical rays. In some fishes with vertebrated tail fins the fin is symmetric, and this seems to be the primitive type.
During the four following months it goes in and out, and strolls about between meals, like other young ones of its class, and is then an animal at nurse affording thus a twofold example of the tendency of the great Creator to repeat Himself in His conceptions, here using for the infancy of the mammal the system invented for adult insects elsewhere repeating the butterfly in the humming-bird, who may fairly be called a vertebrated butterfly, and reproducing the gnat in the vampire-bat, which I look upon as an enlarged and perfected revise of the original pattern, whence comes the scourge of our sweet summer nights.
But if considerations of this kind compel us to place the origin of vertebrated animals at a period sufficiently distant from the Upper Silurian, in which the first Elasmobranchs and Ganoids occur, to allow of the evolution of such fishes as these from a Vertebrate as simple as the Amphioxus, I can only repeat that it is appalling to speculate upon the extent to which that origin must have preceded the epoch of the first recorded appearance of vertebrate life.
To effect this purpose, it made every effort in its power; turning about upon its belly as upon a pivot; snapping its jaws till they cracked like pistol shots; lashing the ground with its long vertebrated tail, till the grass and weeds were swept off as if cut with the blade of a scythe; twisting and wriggling in every possible direction. All to no purpose.
These possess neither brain nor spinal cord; their nerve-centres, instead of being concentrated in a cranium and vertebral canal, are entirely disseminated through the cavities of the trunk, as are the visceral plexuses in vertebrated animals.
Now, in the vertebrated creature, the chest is merely the grand air-receptacle into which the blood is sent to be aërated; while in the insect, the chest contains but its own proportional share of the great air-system.
Too commonly she is an unwholesome stimulant turning a man from wisdom to appearance, from beauty to beautiful pleasures, from form to colour, from persistent aims to belief and stirring triumphs. Arrayed in what she calls distinctly "dress," scented, adorned, displayed, she achieves by artifice a sexual differentiation profounder than that of any other vertebrated animal.
I have now enumerated those characteristic structures of the horse which are of most importance for the purpose we have in view. To any one who is acquainted with the morphology of vertebrated animals, they show that the horse deviates widely from the general structure of mammals; and that the horse type is, in many respects, an extreme modification of the general mammalian plan.
The degree of control is variable, according to the relative predominance of the one or the other; and this predominance varies, not only according to different species of vertebrated animals, but also according to different individuals, in that which presents the most conspicuous capacity for individual variation the human species.
In order to do this effectually, the sides of the body, where the air-mouths are, must be smeared with oil. In the vertebrated animals, the blood is driven through branching tubes to receptacles of air placed within the chest; the air-channels terminate in blood extremities, and the blood-vessels cover these as a net-work.
Word Of The Day