Regeneration 187 



to Boveri*s law which Driesch has actually found had 

 been predicted by Boveri. 



These facts show that the growth of an organ comes 

 to a standstill when a certain size is reached or a certain 

 number of cells are formed. We cannot yet state why 

 this should be, but we are able to add that the formation 

 of a lens of normal size in the regeneration of the eye 

 is in harmony with the phenomena in the embryo. 

 There seems therefore no reason for stating that the 

 regeneration of the lens cannot be explained on a purely 

 physicochemical basis. The only justification for such 

 a statement on the part of Wolf is that he was not in 

 possession of the more complete set of facts now avail- 

 able through the work of Fischel and Uhlenhuth. 



The healing of a wound is a process essentially simi- 

 lar to the regeneration of the lens. Normally the cells 

 which begin to proliferate after a wound is made in the 

 skin lie dormant, inasmuch as they neither grow nor 

 divide. When a wound is made certain layers of 

 epidermal cells undergo rapid cell division. Leo Loeb^ 

 has studied this case extensively. He found that if the 

 skin is removed anywhere, epidermis cells from the 

 wound edge creep upon the denuded spot and form a 

 covering. This may be a tropism (stereotropism) or it 

 may be a mere surface tension phenomenon. Next a 

 rapid process of cell division begins in the cells adjacent 

 to the wound these cells having been heretofore dormant. 



^ Loeb, Leo, Arch. f. Entwcklngsmech., 1898, vi., 297. 



