Regeneration / by Thomas Hunt Morgan.

  • Thomas Hunt Morgan
Date:
1901
Catalogue details

Licence: In copyright

Credit: Regeneration / by Thomas Hunt Morgan. Source: Wellcome Collection.

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    determines the kind of regeneration in antennularia, it is possible that if the regenerating piece were placed on a rotating wheel, the piece might still produce a new stem at the apical end, and roots at the lower end. In an experiment of this sort that I made, the pieces did not, it is true, regenerate at all, but this was probably due not to the change of position in regard to gravity, but to agitation of the water, or to the rubbing of the cut-end against the water. It is also possible that in this form the attachment of the piece at one end may be a factor that may counterbalance the action of gravity. Other factors, such as food, or temperature, or oxygen, appear not to determine the kind of product that results, but only the rapidity with which the change takes place. The salts in solution seem also to act on the rate and extent of the new growth, but possibly other cases may be found in which the kind of regeneration may also be affected by the salts. It is important to find that those animals whose growth and regen- eration are influenced by such external factors as light, gravity, and contact are attached animals that stand in a constant relation to these physical agents. They form only a very small part of the entire number of animals in which regeneration takes place. Animals that constantly move about are not, as a rule, influenced during their growth and regeneration by gravity and contact, and under natural circumstances they are always changing their position in regard to these agents. Temperature, and food, and substances in solution act alike on fixed and free forms, and they are, it appears, both influenced in the same way by these agents. The most signifi- cant fact that has been discovered in connection with the influence of external factors on regeneration is that the same factors that influ- ence the normal growth of the organism also affect in the same way the regeneration. As yet an analysis of the external factors that influence growth has not been made out as completely for animals as for plants, especially in those cases in which the result is determined by several factors at the same time. An examination of the factors that influence regeneration in plants will be made in a later chapter. First, how- ever, the internal factors of regeneration in animals will be consid- ered.
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