"That is more than I can say. I don't know that it wants food. You know that reptiles can live without food a wonderful length of time."
"Really, I begin to think there is more in these little beasts than I ever dreamed of. But it must take a great deal of study to get at these facts."
"Not more than to get at any of the other open secrets of Nature. But, since you are interested, look at these tails as the tadpoles come bobbing against the side of the glass. Do you see how they are covered with little white spots?"
"No."
"Look closer. All over the tail there are tiny, cotton-like spots. Take a lens, if your eye isn't sharp enough. There, now you see them."
"Yes; I see a sort of fluff scattered about."
"That fluff is an immense colony of parasites. Let us place the tadpole under the microscope, and you will see each spot turn out to be a multitude of elegant and active animals, having bodies not unlike a crystal goblet supported on an extremely long and flexible stem, and having round their rim or mouth a range of long, delicate hairs, the motion of which gives a wheel-like aspect, and makes an eddy in the water which brings food to the animal."
"This is really interesting! How active they are! How they shrink up, and then, unwinding their twisted stems, expand again! What's the name of this thing?"
"Vorticella. It may be found growing on water fleas, plants, decayed wood, or these tadpoles. People who study the animalcules are very fond of this Vorticella."
"Well, I never could have believed such a patch of fluff could turn out a sight like this: I could watch it for an hour. But what are those small yellowish things sticking on the side of these parasites?"