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If an earthworm is cut in two will the parts survive?

The power of earthworms to regenerate missing parts/though remarkable, is often exaggerated. For instance, it is repeatedly stated that a tail may grow a new head and a head may grow a new tail. That statement is. only partially true. If an angleworm is cut in two near the middle the front half will usually regenerate another tail that will become normal in ^ length as well as in other respects. The hind half, however, will generally produce a second tail at the mutilated end and the worm will have two tails and no head. Such a worm is incapable of ingesting food and will soon die. Only the fore part of an earthworm has the organs essential to . continued life. The posterior portion contains merely part of the intestines, nerve cords, blood tubes, etc. These creatures have no lungs and breathe through their skin. When only a few of the front segments are cut off the injury is quickly repaired by the remaining part of the worm, although when as many as five or six anterior segments are removed the full number is seldom regenerated. Experiments show that earthworms cut in two behind the nineteenth segment rarely regenerate new heads. When such a posterior portion does regenerate a head the new head is likely to be defective. If a worm is cut in several parts generally only the head end will survive, and then only when this part 1 is not too short. Dr. Thomas H. Morgan, who made extensive researches in the regeneration of parts in earthworms, found no cases of survival of the head ends when the segments were as few as fifteen. When the reproductive organs are removed with the head, the hind part, should it regenerate a head, is incapable of reproduction. These organs lie from the ninth to the fifteenth segment, depending on the species., and once destroyed they cannot be regenerated. If the proper parts are selected, it is possible to graft pieces from several earthworms together to make one long worm. The power to regenerate missing parts is greater in many inferior creatures, such as the flat worms, than it is in common earthworms. .

Posted by on March 19, 2010.

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