162 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



of autonomy, and part in the second one, which is to 

 follow. 



Another important phenomenon of the equifmality of 

 regulation was discovered by Morgan. A species of the 

 flatworra Planaria was found to restore its totality out of 

 small pieces either by regeneration proper, if the pieces 

 were fed, or by a sort of rearrangement of material, on the 

 basis of its harmonious-equipotentiality, if they were kept 

 fasting. It is important to note that here we see one of 

 the conditions determining the choice of the way to 

 restoration, as we also do in the well-known equifinal 

 restitutions of the root in plants, where the behaviour of 

 the organism depends on the distance of the operation-wound 

 from the tip. 1 In Tubularia the actual stage of restitution 

 that has been already reached by the stem when the second 

 operation takes place, may account for the specification of 

 its future organogenesis, but this is not at all clearly 

 ascertained at present. 



Clavellina also shows equifinality in its restitution, as 

 has already been shortly mentioned. The isolated branchial 

 apparatus may restitute itself by retro-differentiation to an 

 indifferent stage followed by renovation ; or it may regenerate 

 the intestine-sac in the proper way. Nothing is known 

 here about the conditions, except perhaps that young in- 

 dividuals seem more apt to follow the first of these two 

 ways, older ones the second ; but there are exceptions to 

 this rule. 



The discussion of other instances of equifinality, though 



1 The root may be restored by regeneration proper, or by the production 

 of adventitious roots, or by one of the side-roots changing its geotropism from 

 horizontal to positive, according to the smaller or greater distance of the 

 wound from the tip. 



