MUTILATION AND REGENERATION 393 



as Allolobophora fcetida was amputated, its regeneration 

 was always perfect; that is, if one, two. three, four, or 

 five segments are removed, exactly the same number 

 were renewed. If, however, six or more were removed, 

 only four or five are regenerated, so that the head is 

 perfected, but the full number of segments behind the 

 head is never reproduced. He found this to be the rule 

 for all the annelids. With regard to the posterior end, 

 he found that when it was amputated, the terminal end 

 contained the new opening of the alimentary canal and 

 that the new segments, of which the full complement 

 always forms, arise in front of this terminal segment, the 

 youngest always being the one immediately in front of it. 



It is well known that the tails and fins of fishes readily 

 regenerate when multilated or amputated. Morgan, 

 in his lecture before the Harvey Society, cited an experi- 

 ment made upon the Pacific coast for the purpose of 

 determining whether salmon returned from the sea to 

 the same rivers in which they were born. The fish 

 used for the experiment, thousands in number, were 

 marked by having a V-shaped piece cut from the tail, 

 but as the tail subsequently regenerated the lost part, 

 the markings were lost and the experiment failed. 



Spallanzani (1768) also experimented with mutilated 

 earth-worms, confirming what Bonnet had found; but 

 went further, for he found that when the tail was cut 

 from a tadpole a new tail grows to take its place. If the 

 tadpole is fed, it grows larger while the tail is growing; 

 if it is not fed, it ceases to grow, but a new tail is formed 

 just the same. Further experiments showed that sala- 

 manders also regenerated amputated tails, including the 

 vertebrae, and that if the leg of one of these animals was 

 cut off, it regenerated; if all four legs were amputated, 

 all four legs were regenerated, either together or in suc- 

 cession as they were removed. The regenerative process 

 proceeds whether the animal be fed or not. If it is well 

 fed, it grows larger and the lost part regenerates; if it 

 is not fed, it grows smaller, but the leg or tail continues 



