Ii6 INDIVIDUALITY IN ORGANISMS 



new head, and, secondly, at the basal end with the 

 formation of a new tail. The new apical region as the 

 region of highest metabolic rate determines the estab- 

 lishment of a new major axial gradient, which has the 

 same direction as the original gradient but possesses a 

 higher rate, and in consequence of these changes the 

 parts of the piece below the new apical region undergo 

 more or less structural change into parts characteristic 

 of more apical levels, until sooner or later a stable con- 

 dition of the gradient is attained, and this determines 

 the completion of reconstruction. 



It can scarcely be doubted that the process of recon- 

 stitution of pieces into new individuals is fundamentally 

 the same in all animals, though it may differ widely in 

 details, with the kind and physiological condition of the 

 individual or piece and the nature of the external con- 

 ditions under which reconstitution occurs. Moreover, 

 it is essentially the same process as reconstitution in 

 plants, in that it consists in the development of a new 

 individual beginning with the apical end. The chief 

 difference is that in animals the development of the new 

 individual is usually closely associated with the cut 

 surface or surfaces, while in plants the reaction of the cells 

 at the cut surface usually does not at once cover it with 

 more or less embryonic rapidly growing cells, as it does in 

 animals, and, since the plant is usually a composite 

 individual^ other apical regions already present become 

 dominant, or new apical regions arise in other parts before 

 a new apical region develops at the cut surface. In 

 some cases, where only a small part of the apical region is 

 removed, a new growing tip develops from the cut 

 surface, and in such cases the formation of the new grow- 



