XXIII 



WHY IS REGENERATION OF PROTOPLASMIC FRAG- 

 MENTS WITHOUT A NUCLEUS DIFFICULT OR 

 IMPOSSIBLE? 1 



IT has been shown with certainty by a series of experi- 

 ments that oxygen is necessary for the development of eggs 

 as well as for the processes of regeneration. The reason 

 for this might be sought, among other things, in the fact 

 that, as I have suggested in two previous papers, synthetical 

 changes are necessary for these processes, and that the syn- 

 theses depend upon the supply of oxygen. 2 It is well known 

 that when a cell is cut into several pieces only the pieces 

 containing a nucleus are capable of regeneration, while the 

 pieces without a nucleus soon disintegrate. This has been 

 interpreted by assuming that the nucleus contains specific 

 formative substances, which it gives off to the protoplasm. 

 This conclusion is, however, not binding. It might well be 

 possible that the nucleus is necessary only for the accomplish- 

 ment of processes of oxidation. The removal of the nucleus 

 would in this case be associated with an inhibition or a 

 decrease in the processes of oxidation. This would suffice 

 to prevent the regeneration of enucleated pieces of the cell. 

 I wish now to test in how far the facts at hand agree with 

 such a hypothesis. 



To bring about oxidations in living tissues the presence 

 of catalytic substances is necessary which either "activate" 

 the atmospheric oxygen, or which render the compounds in 

 the cell capable of taking up atmospheric oxygen more 



1 Archivfiir Entwickelungsmechanik der Organismen, Vol. VIII (1899), p. 689 



2 " Assimilation and Heredity," Monist, 1898. 



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