406 ORGANIC GROWTH sec. 



dog when the gall-duct or a long piece of nerve is cut out it 

 is regenerated is intelligible, because the piece removed is 

 the result of the direct and indirect organising action of the 

 surface exposed by the section, and is continually (in the 

 restorative processes of metabolism) being reformed by that 

 action. 



In reply to this it may be remarked that a part serving a 

 particular purpose may be regenerated sometimes in the in- 

 terior of the body in consequence of simple mechanical con- 

 ditions and simple stimulation — possibly, for instance, a duct 

 conveying a liquid, the contents of which took the same 

 course after it was severed as before. But the idea that after 

 the removal of any part the polarisation of the proximal 

 exposed surface is the cause of its recrescence seems to me 

 sufficiently disproved by the fact that parts of animals can 

 grow again into entire animals. This fact can only be 

 explained on the assumption that all parts of the body, in 

 consequence of an acquired definite growth-tendency, have a 

 share of a definite formative power in the way I have main- 

 tained, although the higher the grade of the animals the more 

 heredity has produced a certain degree of peculiarity in the 

 formative powers of the several parts. All the facts of 

 recrescence, it seems to me, are incontestably in favour of, not 

 against, the heredity of acquired characters. Moreover, 

 Pfliiger himself, at the conclusion of his arguments, has a 

 sentence which at least in a certain sense acknowledc^es the 

 influence of the entire organism in recrescence. " If," he says, 

 " in certain regions of the body, by poisons or injuries, the 

 groups of molecules are disturbed out of their normal arrange- 

 ment and thrown into disorder, then almost the whole body, 

 all of it that remains normal, exerts a constant organising 

 influence until from layer to layer the normal arrangement of 

 the particles is re-established ; each layer imposes a definite 

 law on the one succeeding it and works without intermission 



