MUTILATION AND REGENERATION 391 



which they were suspended, gathered themselves together 

 to form a plasmodium, which after a brief time underwent 

 structural differentiation eventuating in the formation of 

 a new sponge. Later, working in the same manner with 

 certain hydroids, he found that when treated in the same 

 manner i.e., cut up and squeezed through bolting cloth, 

 they behaved similarly in that the cells first clustered 

 together to form a plasmodium, and later underwent dif- 

 ferentiation with the reappearance of the hydroid polyp. 



Mutilated planarians unsegmented worms recover 

 the normal form after mutilation, by the twofold process 

 of rearrangement and growth; rearrangement predominat- 

 ing over growth if the organism cannot feed, growth pre- 

 dominating 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 com- 

 plexity is reached, it ceases and multilation results either 

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



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). 



