MUTILATION AND KEGENERATION 377 



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 

 to regenerate just the same. It takes about as long 

 for the perfect regeneration of the fingers or toes as for 

 an entire limb. If a limb be amputated too close to the 

 body, no regeneration takes place, though the wound 

 heals. In one experiment, Spallanzani amputated all 

 four legs and the tail of a salamander six times and saw 

 them all regenerate six times during the three summer 

 months. He also found that the upper and lower jaws of 

 salamanders can regenerate. Lessona found that terres- 

 trial salamanders cannot regenerate lost parts, though 

 aquatic species of the same genus can do so. Extend- 

 ing these experiments still further, Spallanzani found 

 that snails can regenerate amputated tentacles and 



