swimbladder

Again, an organ may become rudimentary for its proper purpose, and be used for a distinct one: in certain fishes the swimbladder seems to be rudimentary for its proper function of giving buoyancy, but has become converted into a nascent breathing organ or lung.

Darwin and the vermiform appendix - The Panda's Thumb 2009

You can see one ‘error’ in the quote above: we are now pretty certain that the original function of the swimbladder in fish was respiratory.

Darwin and the vermiform appendix - The Panda's Thumb 2009

” This subject is intimately connected with that of the gradation of characters, often accompanied by a change of function, —for instance, the conversion of a swimbladder into lungs, —points which were discussed in the last chapter under two headings.

VII. Miscellaneous Objections to the Theory of Natural Selection 1909

All physiologists admit that the swimbladder is homologous, or “ideally similar” in position and structure with the lungs of the higher vertebrate animals: hence there is no reason to doubt that the swim bladder has actually been converted into lungs, or an organ used exclusively for respiration.

VI. Difficulties of the Theory. Modes of Transition 1909

The Pleuronectidæ whilst very young and still symmetrical, with their eyes standing on opposite sides of the head, cannot long retain a vertical position, owing to the excessive depth of their bodies, the small size of their lateral fins, and to their being destitute of a swimbladder.

VII. Miscellaneous Objections to the Theory of Natural Selection 1909

I can, indeed, hardly doubt that all vertebrate animals having true lungs have descended by ordinary generation from an ancient prototype, of which we know nothing, furnished with a floating apparatus or swimbladder.

On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life 1859

The illustration of the swimbladder in fishes is a good one, because it shows us clearly the highly important fact that an organ originally constructed for one purpose, namely flotation, may be converted into one for a wholly different purpose, namely respiration.

On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life 1859

The swimbladder has, also, been worked in as an accessory to the auditory organs of certain fish, or, for I do not know which view is now generally held, a part of the auditory apparatus has been worked in as a complement to the swimbladder.

On the Origin of Species~ Chapter 06 (historical) Charles Darwin 1859

The swimbladder has, also, been worked in as an accessory to the auditory organs of certain fish, or, for I do not know which view is now generally held, a part of the auditory apparatus has been worked in as a complement to the swimbladder.

On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life 1859

All physiologists admit that the swimbladder is homologous, or 'ideally similar,' in position and structure with the lungs of the higher vertebrate animals: hence there seems to me to be no great difficulty in believing that natural selection has actually converted a swimbladder into a lung, or organ used exclusively for respiration.

On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life 1859