A blade of grass is a mystery, if men would but distill it out. When my learned friend Dr. Syntax, glancing round my workroom, observed a vase full of tadpoles, he asked me in a tone of sniffling superiority: "Do you really mean to say you find any interest in those little beasts?"

"As much as you find in books," I answered, with some energy.

"H'm," grunted Syntax.

Very absurd isn't it? But we all have our hobbies. I can pass a bookstall on which I perceive that the ignorance of the bookseller permits him to exhibit now and then rare editions of valuable books at almost no price at all. The sight gives me no thrill—it does not even cause me to slacken my pace.

But I can't so easily pass a pond in which I see a shoal of tadpoles swimming about, as ignorant of their own value as the bookseller is of his books. I may walk on, but the sight has sent a slight electric shock through me.

"Why, sir," I said to my learned friend, "there is more to me in the tail of one of those tadpoles than in all the musty old volumes you so much delight to pick up. But I won't thrash your dog unless you thrash mine."

"Why, what on earth can you do with the tail?"

"Do with it? Study it, experiment on it, put it under the microscope, and day by day watch the growth of its various parts. At first it is little more than a mass of cells. Then I notice that these cells begin to take a definite shape, and blood vessels appear in them. Then the muscles begin to appear."

"Very interesting, I dare say."

"You don't seem to think so, by your tone. But look in this vase: here are several tadpoles with the most apologetic of tails—mere stumps, in fact. I cut them off nine days ago."

"Will they grow again?"

"Perfectly; for, although the frog dispenses with a tail almost as soon as he reaches the frog form, the tadpole needs his tail to swim with; and when by any accident he loses it, Nature kindly supplies him with another."

"Yes, yes," added Syntax, glad to feel himself once more among things of which he knew something; "just like the lobster or the crab, you know. They tear off their legs and arms in a most reckless way, and yet they always grow new ones again."

"Would you like to know what has become of the tails which I cut off from these fellows?"

"Aren't they dead?"

"Not at all. Alive and kicking." "Alive after nine days? Oh! oh!"

"Here they are, in this glass. It is exactly nine days since they were cut off, and I have been watching them daily under the microscope. I assure you that I have seen them grow, not larger, indeed, but develop more and more, muscle fibers appearing each day where before there were none at all."

"Come, now, you are trying to see what a fool you can make of me."

"I am perfectly serious. The discovery is none of mine. It was made by M. Vulpian in Paris. He says that the tails live many days—as many as eighteen in one instance; but I have never kept mine alive more than eleven. He says, moreover, that they not only grow, as I have said, but that they seem to possess feeling, for they twist about with a rapid swimming movement when irritated."

"Well, but I say, how could they live when separated from the body? Our arms or legs don't live; the lobster's legs don't live."

"Quite true. But in those cases we have limbs of a complex organization, which require a complex apparatus in order to sustain their life. They must have blood, the blood must circulate."

"Stop, stop! I don't want to understand why our arms can't live apart from our bodies. They don't. The fact is enough for me. I want to know why the tail of a tadpole can live apart from the body."

"It can. Is not the fact enough for you in that case also? Well, I was going to tell you the reason. The tail will live apart from the body only so long as it retains its early immature form. If you cut it off from a tadpole which is old enough to have lost its external gills a week or more, the tail will not live more than three or four days. And every tail will die as soon as it reaches the point in its development which requires the circulation of the blood as a necessary condition."

"But where does it get food?"

"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?"

"Those, my dear Syntax, are also parasites."

"What, parasites living on parasites?"

"Why not? Nature is economical. Don't you live on beef, and mutton, and fish? Don't these beeves, muttons, and fishes live on vegetables and animals? Don't the vegetables and animals live on other organic matters? Eat and be eaten, is one law: live and let live, is another."

The learned Doctor remained thoughtful; then he screwed up one side of his face into the most frightful wrinkles, while with the eye of the other he resumed his examination of the Vorticella.