. Elementary biology; an introduction to the science of life . we should certainly never expect to make two whole pigs by cutting one into two parts.^ Among lobsters, crabs, and crayfish the power of regenera- tion is also present in a very high degree. When one of these animals has his claw or one of the legs caught or mutilated, he may throw the limb off com- pletely, the separation taking place along a definite plane between two of the joints. The wound does not bleed and the lost limb is soon replaced by the regeneration of another from the tissues about the scar. 322. Vegetative propagati
. Elementary biology; an introduction to the science of life . we should certainly never expect to make two whole pigs by cutting one into two parts.^ Among lobsters, crabs, and crayfish the power of regenera- tion is also present in a very high degree. When one of these animals has his claw or one of the legs caught or mutilated, he may throw the limb off com- pletely, the separation taking place along a definite plane between two of the joints. The wound does not bleed and the lost limb is soon replaced by the regeneration of another from the tissues about the scar. 322. Vegetative propagation. A stem separated from the root can regenerate roots, as we have already learned (p. 48), Fruit growers propagate new lots of individuals, from trees that are especially desirable, by setting out slips, or cuttings, of these trees and having them "set" roots. In this way all the good qualities of a given tree can be indefinitely extended to a large number of trees. Indeed, we may consider all the cuttings from a single tree as really parts of the tree growing separately. This relation has been described as a discoutimtous grozvtk of a single individual. 1 The growth of the hair or of the finger nails after the ends have been cut off does not represent a case of regeneration. The hair and the nails grow continuously, the live cells in the follicle and in the root of the nail producing new cells which are being pushed forward by the new cells underneath. Cut- ting hair or nails simply removes the external, dead portion of the structure. The new teeth that a child gets after losing the first teeth do not represent regeneration either, since the rudiments of the second teeth are present long before the first teeth drop out. The new teeth are independent structures that develop normally and actually push out the first teeth Fig. 107. Regeneration in starfish The mutilation of starfish does not seem to kill them, for each part may regrow enough to complete a new individu
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