REGENEkATlON 



93 



CHAPTER II 

 REGENERATION 



I. Its Cause and Origin in the Idioplasm 



It does not follow directly from what has already been said 

 with regard to the structure of the germ-plasm, that lost parts 

 can be more or less completely replaced. The only deduction 

 that can be made so far is, that all the parts of which the entire 

 organism is composed are formed once during the development 

 of the organism from the ^g'g : no explanation is given of the 

 fact that individual parts can be produced a second time, when 

 they have been lost by the action of external influences. During 

 ontogeny, the determinants of the part in question pass from the 

 ovum into the segmentation-cells, from these into embryonic 

 cells of a later stage, and finally into those cells which constitute 

 the fully formed part. If tliis part is forcibly removed from the 

 organism to which it belongs, its determinants are removed 

 along with it : this follows from what has already been assumed 

 with regard to the ontogenetic stages of the idioplasm. We 

 must now' therefore attempt to explain the fact that a part of the 

 body can nevertheless be reconstructed. 



If the capacity for regeneration were possible at all, it is 

 obvious that it would have to be introduced by Nature, for its 

 physiological importance is apparent. The power of replacing 

 larger or smaller parts of the body must in all cases be useful to 

 the organism, and is often indeed indispensable to its further 

 existence. Arnold Lang * is certainly right in considering the 

 faculty of regeneration in animals to be one of the arrangements 

 for protection which prevent the species from perishing. The 

 capability of completely restoring those parts of the body which 

 have become injured by the bite of an enemy, forms a more 



* ' Ueberden Einfluss der fesfsitzenden Lebensweise auf die Thiere,' &c. 

 Jena, 1888, p. 108. 



