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Turbot, plaice, and other flat-fish, which have no swim-bladder, lie with one side in the mud at the bottom of the sea or rivers Can you guess in which side of the head their eyes are placed? "In the uppermost, and sometimes both eyes are there." You are right, for there would be no use for an eye in the side turned to the mud.
Scientific interest and filial piety ought alike to secure our attention for the African mud-fish. It lives its amphibious life among the rice-fields on the Nile, the Zambesi, and the Gambia, and is so greatly given to a terrestrial existence that its swim-bladder has become porous and cellular, so as to be modified into a pair of true and serviceable lungs.
According to this view it may be inferred that all vertebrate animals with true lungs are descended by ordinary generation from an ancient and unknown prototype which was furnished with a floating apparatus or swim-bladder.
I can indeed hardly doubt that all vertebrate animals having true lungs have descended by ordinary generation from the ancient prototype, of which we know nothing, furnished with a floating apparatus or swim-bladder p. 191. We must be cautious
The swim-bladder which we have just described in other fishes is, with this lungfish, peculiarly spongy in its walls, presenting a large surface full of blood vessels which absorb the air on the inside of the bladder. This air the fish changes with moderate frequency, the result being that the swim-bladder serves him exactly as the lung serves a higher animal.
In many it has been converted into the swim-bladder, and in this form serves a useful purpose, but varies very greatly in shape and size. Finally, in a few instances, it retains some measure of its probably original function of air-breathing.
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.
Then came a day when one of these huge, amiable, living smiles blundered into our net, a smile a foot wide and six feet long, and even as he lay quietly awaiting what fate brought to great catfish, he sang, both theme and accompaniment. His whole being throbbed with the continuous deep drumming as the thin, silky walls of his swim-bladder vibrated in the depths of his body.
Lungs, enlargement of, in the Quichua and Aymara Indians; a modified swim-bladder; different capacity of, in races of man. Luschka, Prof., on the termination of the coccyx. Luxury, expectation of life uninfluenced by. Lycaena, sexual differences of colour in species of. Lycaenae, colours of.
It is an interesting fact that when the lung begins to form in the embryo it starts as a simple sac which is an offspring from the gullet, and occupies the position of the swim-bladder of the fish. This sac later divides into two, and develops into the lungs of the animal.
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