REGENERATION AND LIABILITY TO INJURY. 



T. H. MORGAN. 



IT is not uncommon to meet with the statement that there 

 exists a relation between the power of regeneration of a part 

 and its liability to injury. Certain well-established facts in 

 regard to the regeneration of internal organs are entirely over- 

 looked or disregarded in the attempt to show that the above 

 relation "explains" the origin of regeneration. It would be 

 interesting if those who hold that "there is no such thing as a 

 general power of regeneration; in each kind of animal this 

 power is graduated according to the need of regeneration in the 

 part under consideration," - it would be interesting if such 

 persons would show how such a thing could arise by means of 

 "variation " and "survival of the fittest." 



True, Weismann has given rather an elaborate explanation 

 of his view of the matter; but I cannot believe that the chapter 

 on regeneration in the Germ-Plasm will convince any one that 

 the phenomena are in any way explained. For myself, I fail to 

 see by what nice mechanism the power of regeneration is grad- 

 uated according to the need of regeneration of each part. The 

 " Natur-philosophie " seems not yet dead. 



The following pages contain an account of some experiments 

 made at Woods Roll, Mass., at the Marine Biological Laboratory 

 during the summer of 1897, on the power of regeneration of the 

 different appendages of the common hermit crab (Eupagurus 

 longicarpits). A part of the animal is protected by the appropri- 

 ated shell of a mollusc, and the appendages are modified in con- 

 nection with the peculiar habitat of the animal. The anterior 

 appendages are exposed, and some of them are not infrequently 

 lost ; while the appendages protected by the shell do not seem 

 to be often injured. The results are treated under the following 

 headings: 



