“Life on Earth” [a 12-part TV series on evolution] was easier than “The Living Planet” because you have 2,000 years of narrative thrust built in. … You begin, say, with a giant jellyfish, then a fish with lungs which then became a frog. And all you have to do is say, “If you want to know what happens next, tune in next week.”

[As Chief Scientific Adviser to the British Ministry of Defence] We persist in regarding ourselves as a Great Power, capable of everything and only temporarily handicapped by economic difficulties. We are not a great power and never will be again. We are a great nation, but if we continue to behave like a Great Power we shall soon cease to be a great nation. Let us take warning from the fate of the Great Powers of the past and not burst ourselves with pride (see Aesop’s fable of the frog). (1949)

[When recording electrical impulses from a frog nerve-muscle preparation seemed to show a tiresomely oscillating electrical artefact—but only when the muscle was hanging unsupported.] The explanation suddenly dawned on me ... a muscle hanging under its own weight ought, if you come to think of it, to be sending sensory impulses up the nerves coming from the muscle spindles ... That particular day’s work, I think, had all the elements that one could wish for. The new apparatus seemed to be misbehaving very badly indeed, and I suddenly found it was behaving so well that it was opening up an entire new range of data ... it didn’t involve any particular hard work, or any particular intelligence on my part. It was just one of those things which sometimes happens in a laboratory if you stick apparatus together and see what results you get.

Interviewer: Is there any science that’s not wrapped in politics?
Seitz: Oh, there are some things. The disappearance of the frog—as you know, the frog is dying worldwide. … I don’t think that has had any political repercussions other than the fact that that is happening.

Le biologiste passe, la grenouille reste.
The biologist passes, the frog remains.
[Sometimes quoted as “Theories pass. The frog remains.”]

Adam is fading out. It is on account of Darwin and that crowd. I can see that he is not going to last much longer. There's a plenty of signs. He is getting belittled to a germ—a little bit of a speck that you can't see without a microscope powerful enough to raise a gnat to the size of a church. They take that speck and breed from it: first a flea; then a fly, then a bug, then cross these and get a fish, then a raft of fishes, all kinds, then cross the whole lot and get a reptile, then work up the reptiles till you've got a supply of lizards and spiders and toads and alligators and Congressmen and so on, then cross the entire lot again and get a plant of amphibiums, which are half-breeds and do business both wet and dry, such as turtles and frogs and ornithorhyncuses and so on, and cross-up again and get a mongrel bird, sired by a snake and dam'd by a bat, resulting in a pterodactyl, then they develop him, and water his stock till they've got the air filled with a million things that wear feathers, then they cross-up all the accumulated animal life to date and fetch out a mammal, and start-in diluting again till there's cows and tigers and rats and elephants and monkeys and everything you want down to the Missing Link, and out of him and a mermaid they propagate Man, and there you are! Everything ship-shape and finished-up, and nothing to do but lay low and wait and see if it was worth the time and expense.

An engineer passing a pond heard a frog say, “If you kiss me, I’ll turn into a beautiful princess.” He picked up the frog, looked at it, and put it in his pocket. The frog said, “Why didn’t you kiss me?” Replied the engineer, “Look, I’m an engineer. I don’t have time for a girlfriend, but a talking frog is cool.”

Do you think that the amoeba ever dreamed that it would evolve into the frog? Of course it didn’t. And when that first frog shimmied out of the water and employed its vocal chords in order to attract a mate or to retard a predator, do you think that that frog ever imagined that that incipient croak would evolve into all the languages of the world, into all the literature of the world? Of course it … didn’t. And just as that froggy could never possibly have conceived of Shakespeare, so we can never possibly imagine our destiny.

Don't be impatient with me. Bear in mind that I hop around among all of you big beasts like a harmless and helpless frog who is afraid of being squashed.

Evolution is a hard, inescapable mistress. There is just no room for compassion or good sportsmanship. Too many organisms are born, so, quite simply, a lot of them are going to have to die because there isn't enough food and space to go around. You can be beautiful, fast and strong, but it might not matter. The only thing that does matter is, whether you leave more children carrying your genes than the next person leaves. It’s true whether you’re a prince, a frog, or an American elm.

FROG, n. A reptile with edible legs

Frogs will eat red-flannel worms fed to them by biologists; this proves a great deal about both parties concerned.

Humor can be dissected, as a frog can, but the thing dies in the process and the innards are discouraging to any but the purely scientific mind.

I am a naturalist rather than a scientist. Simply looking at a flower or a frog has always seemed to me to be just about the most interesting thing there is. Others say human beings are pretty interesting, which they are, but as a child you’re not interested in Auntie Flo’s psychology; you’re interested in how a dragonfly larva turns into a dragonfly.

I feel like a white granular mass of amorphous crystals—my formula appears to be isomeric with Spasmotoxin. My aurochloride precipitates into beautiful prismatic needles. My Platinochloride develops octohedron crystals,—with fine blue florescence. My physiological action is not indifferent. One millionth of a grain injected under the skin of a frog produced instantaneous death accompanied by an orange blossom odor. The heart stopped in systole. A base—L₃H₉NG₄—offers analogous reaction to phosmotinigstic acid.

I have destroyed almost the whole race of frogs, which does not happen in that savage Batrachomyomachia of Homer. For in the anatomy of frogs, which, by favour of my very excellent colleague D. Carolo Fracassato, I had set on foot in order to become more certain about the membranous substance of the lungs, it happened to me to see such things that not undeservedly I can better make use of that [saying] of Homer for the present matter—
“I see with my eyes a work trusty and great.”
For in this (frog anatomy) owing to the simplicity of the structure, and the almost complete transparency of the vessels which admits the eye into the interior, things are more clearly shown so that they will bring the light to other more obscure matters.

I have found that a measurable period of time elapses before the stimulus applied to the iliac plexus of the frog is transmitted to the insertion of the crural nerve into the gastrocnemius muscle by a brief electric current. In large frogs, in which the nerves were from 50-60 mm. in length, and which were preserved at a temperature of 2-6° C, although the temperature of the observation chanber was between 11° and 150° C, the elapsed time was 0.0014 to 0.0020 of a second.

I have known silence: the cold earthy silence at the bottom of a newly dug well; the implacable stony silence of a deep cave; the hot, drugged midday silence when everything is hypnotised and stilled into silence by the eye of the sun;… I have heard summer cicadas cry so that the sound seems stitched into your bones. I have heard tree frogs in an orchestration as complicated as Bach singing in a forest lit by a million emerald fireflies. I have heard the Keas calling over grey glaciers that groaned to themselves like old people as they inched their way to the sea. I have heard the hoarse street vendor cries of the mating Fur seals as they sang to their sleek golden wives, the crisp staccato admonishment of the Rattlesnake, the cobweb squeak of the Bat and the belling roar of the Red deer knee-deep in purple heather.

I noticed affixed to a laboratory door the following words: “Les théories passent. Le Grenouille reste. [The theories pass. The frog remains.] &mdashJean Rostand, Carnets d’un biologiste.” There is a risk that in the less severe discipline of criticism the result may turn out to be different; the theories will remain but the frog may disappear.

I should object to any experimentation which can justly be called painful, for the purpose of elementary instruction ... [but I regret] a condition of the law which permits a boy to troll for pike, or set lines with live frog bait, for idle amusement; and, at the same time, lays the teacher of that boy open to the penalty of fine and imprisonment, if he uses the same animal for the purpose of exhibiting one of the most beautiful and instructive of physiological spectacles, the circulation in the web of the foot. ... [Maybe the frog is] inconvenienced by being wrapped up in a wet rag, and having his toes tied out ... But you must not inflict the least pain on a vertebrated animal for scientific purposes (though you may do a good deal in that way for gain or for sport) without due licence of the Secretary of State for the Home Department, granted under the authority of the Vivisection Act.
... [Yet, in] 1877, two persons may be charged with cruelty to animals. One has impaled a frog, and suffered the creature to writhe about in that condition for hours; the other has pained the animal no more than one of us would be pained by tying strings round his fingers, and keeping him in the position of a hydropathic patient. The first offender says, 'I did it because I find fishing very amusing,' and the magistrate bids him depart in peace; nay, probably wishes him good sport. The second pleads, 'I wanted to impress a scientific truth, with a distinctness attainable in no other way, on the minds of my scholars,' and the magistrate fines him five pounds.
I cannot but think that this is an anomalous and not wholly creditable state of things.

If there is an underlying oneness of all things, it does not matter where we begin, whether with stars, or laws of supply and demand, or frogs, or Napoleon Bonaparte. One measures a circle, beginning anywhere.

Is man a peculiar organism? Does he originate in a wholly different way from a dog, bird, frog, or fish? and does he thereby justify those who assert that he has no place in nature, and no real relationship with the lower world of animal life? Or does he develop from a similar embryo, and undergo the same slow and gradual progressive modifications? The answer is not for an instant doubtful, and has not been doubtful for the last thirty years. The mode of man’s origin and the earlier stages of his development are undoubtedly identical with those of the animals standing directly below him in the scale; without the slightest doubt, he stands in this respect nearer the ape than the ape does to the dog. (1863)

Many persons nowadays seem to think that any conclusion must be very scientific if the arguments in favor of it are derived from twitching of frogs’ legs—especially if the frogs are decapitated—and that—on the other hand—any doctrine chiefly vouched for by the feelings of human beings—with heads on their shoulders—must be benighted and superstitious.

Now come the minstrels of the swamp and pool,
The peeping frogs who make the marshes ring
At sundown like some myriad-squeaking thing!
Thus with our senses Nature plays the fool.

On entering his [John James Audubon] room, I was astonished and delighted to find that it was turned into a museum. The walls were festooned with all kinds of birds’ eggs, carefully blown out and strung on a thread. The chimney-piece was covered with stuffed squirrels, raccoons, and opossums; and the shelves around were likewise crowded with specimens, among which were fishes, frogs, snakes, lizards, and other reptiles. Besides these stuffed varieties, many paintings were arrayed on the walls, chiefly of birds.

One day a math-deficient frog was sitting on a tiny lily pad in a big pond—a lily pad that doubled in size each night—and on this day the pad covered just one-eighth of the pond. The frog still saw the vast majority of his beloved water and so was unconcerned. Then, just three days later, he woke to find the pond had vanished while he slept.

One of the most curious and interesting reptiles which I met with in Borneo was a large tree-frog, which was brought me by one of the Chinese workmen. He assured me that he had seen it come down in a slanting direction from a high tree, as if it flew. On examining it, I found the toes very long and fully webbed to their very extremity, so that when expanded they offered a surface much larger than the body. The forelegs were also bordered by a membrane, and the body was capable of considerable inflation. The back and limbs were of a very deep shining green colour, the undersurface and the inner toes yellow, while the webs were black, rayed with yellow. The body was about four inches long, while the webs of each hind foot, when fully expanded, covered a surface of four square inches, and the webs of all the feet together about twelve square inches. As the extremities of the toes have dilated discs for adhesion, showing the creature to be a true tree frog, it is difficult to imagine that this immense membrane of the toes can be for the purpose of swimming only, and the account of the Chinaman, that it flew down from the tree, becomes more credible. This is, I believe, the first instance known of a “flying frog,” and it is very interesting to Darwinians as showing that the variability of the toes which have been already modified for purposes of swimming and adhesive climbing, have been taken advantage of to enable an allied species to pass through the air like the flying lizard. It would appear to be a new species of the genus Rhacophorus, which consists of several frogs of a much smaller size than this, and having the webs of the toes less developed.

Poison should be tried out on a frog.

The bird which is drawn to the water by its need of finding there the prey on which it lives, separates the digits of its feet in trying to strike the water and move about on the surface. The skin which unites these digits at their base acquires the habit of being stretched by these continually repeated separations of the digits; thus in course of time there are formed large webs which unite the digits of ducks, geese, etc., as we actually find them. In the same way efforts to swim, that is to push against the water so as to move about in it, have stretched the membranes between the digits of frogs, sea-tortoises, the otter, beaver, etc.
On the other hand, a bird which is accustomed to perch on trees and which springs from individuals all of whom had acquired this habit, necessarily has longer digits on its feet and differently shaped from those of the aquatic animals that I have just named. Its claws in time become lengthened, sharpened and curved into hooks, to clasp the branches on which the animal so often rests.
We find in the same way that the bird of the water-side which does not like swimming and yet is in need of going to the water's edge to secure its prey, is continually liable to sink into the mud. Now this bird tries to act in such a way that its body should not be immersed in the liquid, and hence makes its best efforts to stretch and lengthen its legs. The long-established habit acquired by this bird and all its race of continually stretching and lengthening its legs, results in the individuals of this race becoming raised as though on stilts, and gradually obtaining long, bare legs, denuded of feathers up to the thighs and often higher still.

The extracellular genesis of cells in animals seemed to me, ever since the publication of the cell theory [of Schwann], just as unlikely as the spontaneous generation of organisms. These doubts produced my observations on the multiplication of blood cells by division in bird and mammalian embryos and on the division of muscle bundles in frog larvae. Since then I have continued these observations in frog larvae, where it is possible to follow the history of tissues back to segmentation.

The Frog—that arch-martyr to science—affords the most convenient subject.

The night before Easter Sunday of that year (1920) I awoke, turned on the light, and jotted down a few notes on a tiny slip of thin paper. Then I fell asleep again. It occurred to me at six o’clock in the morning that during the night I had written down something most important, but I was unable to decipher the scrawl. The next night, at three o’clock, the idea returned. It was the design of an experiment to determine whether the hypothesis of chemical transmission that I had uttered seventeen years ago was correct. I got up immediately, went to the laboratory, and performed a simple experiment on a frog heart according to the nocturnal design. I have to describe this experiment briefly since its results became the foundation of the theory of chemical transmission of the nervous impulse. The hearts of two frogs were isolated, the first with its nerves, the second without. Both hearts were attached to Straub cannulas filled with a little Ringer solution. The vagus nerve of the first heart was stimulated for a few minutes. Then the Ringer solution that had been in the first heart during the stimulation of the vagus was transferred to the second heart. It slowed and its beats diminished just as if its vagus had been stimulated. Similarly, when the accelerator nerve was stimulated and the Ringer from this period transferred, the second heart speeded up and its beats increased. These results unequivocally proved that the nerves do not influence the heart directly but liberate from their terminals specific chemical substances which, in their turn, cause the well-known modifications of the function of the heart characteristic of the stimulation of its nerves.

The power of the eye could not be extended further in the opened living animal, hence I had believed that this body of the blood breaks into the empty space, and is collected again by a gaping vessel and by the structure of the walls. The tortuous and diffused motion of the blood in divers directions, and its union at a determinate place offered a handle to this. But the dried lung of the frog made my belief dubious. This lung had, by chance, preserved the redness of the blood in (what afterwards proved to be) the smallest vessels, where by means of a more perfect lens, no more there met the eye the points forming the skin called Sagrino, but vessels mingled annularly. And, so great is the divarication of these vessels as they go out, here from a vein, there from an artery, that order is no longer preserved, but a network appears made up of the prolongations of both vessels. This network occupies not only the whole floor, but extends also to the walls, and is attached to the outgoing vessel, as I could see with greater difficulty but more abundantly in the oblong lung of a tortoise, which is similarly membranous and transparent. Here it was clear to sense that the blood flows away through the tortuous vessels, that it is not poured into spaces but always works through tubules, and is dispersed by the multiplex winding of the vessels.

The symbol A is not the counterpart of anything in familiar life. To the child the letter A would seem horribly abstract; so we give him a familiar conception along with it. “A was an Archer who shot at a frog.” This tides over his immediate difficulty; but he cannot make serious progress with word-building so long as Archers, Butchers, Captains, dance round the letters. The letters are abstract, and sooner or later he has to realise it. In physics we have outgrown archer and apple-pie definitions of the fundamental symbols. To a request to explain what an electron really is supposed to be we can only answer, “It is part of the A B C of physics”.

There must be a marsh in the brains of these men or there would not be so many frogs of wrong ideas gathered in their heads.

Three hundred trout are needed to support one man for a year. The trout, in turn, must consume 90,000 frogs, that must consume 27 million grasshoppers that live off of 1,000 tons of grass.

We spend long hours discussing the curious situation that the two great bodies of biological knowledge, genetics and embryology, which were obviously intimately interrelated in development, had never been brought together in any revealing way. An obvious difficulty was that the most favorable organisms for genetics, Drosophila as a prime example, were not well suited for embryological study, and the classical objects of embryological study, sea urchins and frogs as examples, were not easily investigated genetically. What might we do about it? There were two obvious approaches: one to learn more about the genetics of an embryologically favourable organism, the other to better understand the development of Drosophila. We resolved to gamble up to a year of our lives on the latter approach, this in Ephrussi’s laboratory in Paris which was admirably equipped for tissue culture, tissue or organ transplantation, and related techniques.

Well, basically, there was this little dot, right? And the dot went bang and the bang expanded. Energy formed into matter, matter cooled, matter lived, the amoeba to fish, to fish to fowl, to fowl to frog, to frog to mammal, the mammal to monkey, to monkey to man, amo amas amat, quid pro quo, memento mori, ad infinitum, sprinkle on a little bit of grated cheese and leave under the grill till Doomsday.

What happens if a big asteroid hits Earth? Judging from realistic simulations involving a sledge hammer and a common laboratory frog, we can assume it will be pretty bad.

What is this frog and mouse battle among the mathematicians?

When by night the frogs are croaking, kindle but a torch’s fire,
Ha! how soon they all are silent! Thus Truth silences the liar.

Why it is that animals, instead of developing in a simple and straightforward way, undergo in the course of their growth a series of complicated changes, during which they often acquire organs which have no function, and which, after remaining visible for a short time, disappear without leaving a trace ... To the Darwinian, the explanation of such facts is obvious. The stage when the tadpole breathes by gills is a repetition of the stage when the ancestors of the frog had not advanced in the scale of development beyond a fish.

You can’t discuss the ocean with a well frog—he’s limited by the space he lives in. [A frog in a well cannot conceive of the ocean.]

You don’t ask the frogs when you drain the marsh.