The Biological Bulletin Volume 6

The Biological Bulletin Volume 6

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 edition. Excerpt: ... forms. If it is subject to greater injury, then it has not acquired the power to meet the situation as have the other species. Considerations of this kind do not have, I believe, any real bearing on the question of whether an organism has or has not acquired the power to regenerate, although some biologists lay great stress on this sort of speculation. The limitations in the power of regeneration of Dendroccelum are peculiar. Lillie found that when only the anterior end of the worm is cut off a new anterior end is regenerated. This power to produce a new head was found to extend back to about one-third of the length of the worm, i. e., to a region just in front of the pharynx. Behind this level the posterior piece fails to regenerate a head at its anterior end. On the other hand, the anterior pieces regenerate a new posterior end from any level, with the possible exception of the iimmediate region of the head itself; but the latter point has not yet been sufficiently examined in this species. It appears a remarkable fact that this planarian should have such extensive powers of regenerating posteriorly, and such limited powers of regenerating anteriorly, especially since, as far as we know, the same cells produce either a head or a tail according to which end is exposed; but this has not been definitely determined, and would be almost impossible to determine with absolute certainty. Eugen Schultz has also studied the regeneration of Dendroccelum lacteum of Europe 1 and finds that posterior pieces do sometimes regenerate a head, although the regeneration is very slow, and it may appear that Lillie did not keep his pieces a sufficiently long time for the regeneration to take place. He states, in fact, that most of the posterior pieces died...
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Product details

  • Paperback
  • 189 x 246 x 6mm | 204g
  • United States
  • English
  • black & white illustrations
  • 1236781597
  • 9781236781598