United States or Martinique ? Vote for the TOP Country of the Week !
And so far as zoological science goes we must, at least, admit that such a creature is an evolutionary possibility. Their kindred, the Gastropods, have, in the case of the snail and slug, learnt the trick of air-breathing.
Physiologists wish to know how the sudden compression of the air in the lungs in plunging to this depth and the equally sudden expansion of it in rising from such a depth is dealt with in the whale's economy, so as to prevent the absolutely deadly results which would ensue were any ordinary air-breathing animal subjected to such changes of pressure.
They also bestow greater care upon their offspring than most of the Fishes. The Birds are warm-blooded and air-breathing, having a double circulation; they are egg-laying like the two other classes, but their eggs are comparatively few in number, and the young are hatched by the mother and fed by the parent birds till they can provide for themselves.
From amoeba and other infusorial animals of simplest structure, through coral and oyster, bird, reptile, to mammals, there is an evident gradation, many structures being represented in entire great groups of living beings, such as the air-breathing lung. Here is a grand plan of animal life, which permits us to classify all living things into a system.
The unsophisticated aborigines knew it as barramunda; the almost equally ignorant white settlers called it with irreverent and unfilial contempt the flat-head. On further examination, however, the despised barramunda proved to be a connecting link of primary rank between the oldest surviving group of fishes and the lowest air-breathing animals like the frogs and salamanders.
Four tiny legs appeared from under its skin, the gills gave place to air-breathing lungs, and the infant lips to a great, gaping mouth. Now, during this "temporary alteration of the premises" all business was of necessity stopped. The half-fish, half-frog could neither sup like an infant nor eat like a man.
Let us remember, then, that, in the Silurian period, the world, so far as it was raised above the ocean, was a beach, and let us seek there for such creatures as God has made to live on sea-shores, and not belittle the Creative work, or say that He first scattered the seeds of life in meagre or stinted measure, because we do not find air-breathing animals when there was no fitting atmosphere to feed their lungs, insects with no terrestrial plants to live upon, reptiles without marshes, birds without trees, cattle without grass, all things, in short, without the essential conditions for their existence.
In the cases in which we know of no intermediate or transitional states, we should be very cautious in concluding that none could have existed, for the homologies of many organs and their intermediate states show that wonderful metamorphoses in function are at least possible. For instance, a swim-bladder has apparently been converted into an air-breathing lung.
We find in the Carboniferous period fossilised remains of five-toed amphibia, the oldest terrestrial, air-breathing vertebrates. These amphibia increase in variety in the Permian epoch. Towards the close of it we find the first Amniotes, the ancestors of the three higher classes of Vertebrates.
So important an advantage would be fostered, and, as the inland sea became smaller, or its population larger or fiercer, the fishes with a sufficiently developed air-breathing apparatus passed to the land, where, as yet, they would find no serious enemy. The fact is beyond dispute; the theory of how it occurred is plausible enough; the consequences were momentous.
Word Of The Day