Biology Hydra Introduction Concerning Green Weeds An account of the discovery of the hydra on the roots of a green water plant. Anthony Von Leeuwenoek (1632-1723) hardly needs an introduction. He is well known for his handmade microscopes; for his discovery of bacteria, protozoa, and sundry other tiny organisms. After 1674, when lie sent his first letter to the Royal Society of London, he was a steady correspondent. His long letters, with their exact and detailed descriptions, were well known to the members of the society. And now in 1703, another document arrived from this skilled reporter, detailing some observations he had made on certain small green plants. These little plants grow on the surface of many shallow ponds. When seen from a distance, the pond may look like a shimmering sheet of green. But on close examination, one can see that the green covering is really composed of thousands and thousands of tiny, discrete, roundish discs, each with a few delicate strands of root-like structures trailing downward in the water. The tiny green discs are often joined together in clusters, as though some discs were budding out of others. These green weeds are known today, as duckweed (Lemna polyrhiza). When Leeuwenoek first observed them, lie also discovered a whole menagerie of tiny animalcules. These lie faithfully portrayed In the figure, ABCDEFGH represents one of these that was fastened to the root of the green weeds. . . . A is the tail with which it fastens itself. CDE represents eight horns, though other specimens that were smaller had only six. The animalcule is drawn as stretched out at its whole length. But when contracted it was not a quarter as long. The horns had a very curious appearance. . . . It was most surprising to see to what great length these animalcula would sometimes extend their horns. Through the microsocope they seemed several fathoms long. . . . They were covered with knotty protuberances that seemed to be composed of seven round globules placed together. . . . When the body was extended . . . I observed somewhere around the middle . . . another of the same kind, but smaller. The tail of the smaller seemed to be fastened to the other at a point which I thought to be the lower part of its belly. In the figure, BH shows the smaller animalculum coming out of the body of the larger. I thought at first that this might be a young animalculum fastened by chance to an old one. But observing it more narrowly, I saw that it was a part of the other. When I first discovered this animalculum, it had only four very small horns. But 16 hours later it was grown much larger both in horns and in body. And four hours after that, it separated completely from its mother's body In the discovery of the young animalculum just describe I had observed on the other side of the body of the largest specimen, a small round knob. . . . In a few hours it grew larger, until it looked like GI in the figure. . . . In thirteen or fourteen hours, it grew so large, that you could see two horns on it. In 24 hours, it had acquired four horns, one of which was small, the second larger, and two Others very large. These last two were more strongly protruded and contracted than the smaller ones. Three hours later, the little animalculum was got clear of its mother. I endeavored to Pursue my discovery of the generation of these creatures. In order to do so, I separated the green weeds from the larger mass to be able to observe better. I now discovered the animalculum not only dead, but his horns and part of his body were quite wasted. I observed in the green weeds abundance of strange animalcula. . . . Sections are excerpts from Philosophical Transactions of the Royal Society of London, 1703, Vol. 23, #283, Concerning Green Weeds Growing in Water, and Some Animalcula about Them," by Anthony Von Leeuwenhoek and #288, "Remarks on M. Leeuwenhoek's Observations on Green Weeds and Animalcula," Anonymous. However, it was not long before his discovery was verified by another member of the Royal Society, whose name does not appear in the record, even though his remarks are recorded in #288 of the Philosophical Transactions for 1703. (The diagrams to which the writer refers appear in Figure below.) I observed the same animalculum Mr. Leeuwenhoek speaks of in #283 of the transactions. I found it at the beginning of the month (June) in some clear water which I took up in a ditch. Despite my utmost attention, I could discover no more than this single one of the same kind. Figure 1 represents it in one of the postures it displayed the first day. The knob at A, which looked like I pouch sticking out of the gut, was something quite different. Two days after, I could perceive two or three white fibers at the extremity of it. On the fourth day, the animal lying stretched at its full length appeared as in Figure 2. 1 plainly saw that it was a young one with six horns, coming out of the side of the old one. The next day, I found it in the water entirely separated from the body, being about one-third the length of the parent. The formation of the horns are well represented by Mr. Leeuwenhoek. They issue like radii, not from the extremity, but around a small knob, which I take to be the head. The horns have a vermicular motion, and are extended or shortened both together and separately. The other extremity is flat, and is often fixed like a leech to the bottom or side of the glass in which I kept it. The animalculum contracts and dilates its body at pleasure. When touched or disturbed the body and horns are both brought into a small compass, so that it has the appearance in Figures 3 and 4. The horns are perfectly white, and the body yellowish. The animal in the water is not easily visible to the naked eye because when extended it is no thicker than a horse-hair. Question: What statements within this text give evidence for this creature to be considered living? An animal?