CHAPTER VI 



AUTOTOMY AND REGENERATION IN ShORE AnIMALS 



A GREAT many animals are well known to have the faculty 

 of growing anew, or regenerating, portions of the body 

 which have been lost as the result of an accident or of the 

 attacks of other animals. Extreme cases are those in which 

 an entirely new individual may be reconstructed from a 

 relatively small portion of the body that has been left, or 

 where, the body having been divided into two or more 

 portions, as many new individuals are regenerated as there 

 were segments resulting from the division. To give an 

 example : worms, of all kinds, have very considerable 

 powers of regeneration. One of the earliest experimenters. 

 Bonnet, cut a fresh- water worm into as many as fourteen 

 pieces and found that each piece produced a new worm, 

 the anterior end in each case growing a new head and the 

 posterior end a new tail. However much our ideas may 

 vary as to the significance of regeneration, we seem safe in 

 supposing that so marked a capacity for regrowth is correlated 

 with the lowly and undifferentiated organisation of these 

 forms. Broadly speaking, the higher we proceed up the 

 animal scale the less the amount of regeneration that is 

 encountered, until, in the highest vertebrates, such power 

 does not extend beyond the healing of comparatively simple 

 wounds. This rule is, however, by no means without 

 exceptions, some of the most striking cases of regeneration 

 occurring among vertebrates. Newts of the genus Triton, 

 for instance, can regrow both their legs and tail : in a famous 

 experiment Spallanzani caused one of these animals to 

 regrow its legs six times. 



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