MUTILATION AND REGENERATION 375 



if the organism cannot feed, growth predominating 

 over rearrangement if it can. 



It goes without saying that this form of regeneration 

 is only possible when the structure of the organism 

 is relatively simple. So soon as a certain degree of 

 complexity is reached, it ceases and multilation results 

 either in repair or in the restoration of the lost part. 



II. The mutilated organism grows a new part to take 

 the place of that which has been lost. 



This form of regeneration is interesting because it 

 takes place through influences that cannot, at present, 

 be clearly understood. 



Morgan, in his book on "Regeneration," makes these 

 divisions of the subject: 



I. Homomorphosis. The new part is like the part 

 removed. 



1. Holomorphosis. The entire part is replaced. 



2. Meromorphosis. The new part is less than 

 that lost. 



II. Heteromorphosis. The new part is different from 

 that removed. 



1. The new part is a mirror figure of that lost. 



2. The new part resembles some other part 

 than that lost. 



3. The new part is unlike anything in the 

 body (Neomorphosis). 



Other descriptive terms used by Morgan are Epi- 

 morphosis, in which a proliferation of new material pre- 

 cedes the development of the new part, and Morpha- 

 laxis, in which the part is transformed directly into the 

 part. 



So far as is known, the first observations upon the 

 regeneration of lost parts was made by Bonnet, who, in 

 1741, experimented with earth-worms. When he cut 

 a common earth-worm in half, the anterior half grew new 

 segments, forming a new tail, and the posterior half 

 new segments and a new head, so that eventually two 

 entire worms resulted. The regenerative capacity was 



