Regeneration of Protoplasts After Wounding 139 



in young tissue-cells combine into one large vacuole dur- 

 ing the rapid growth in the transition to the adult con- 

 dition. When two or more like protoplasts unite to form 

 a so-called symplast, something similar takes place in 

 their walls, at least in some cases, as in the plasmatic 

 membrane and the granular plasm. The ontogeny of the 

 latex-vessels teaches this more clearly than anything else. 

 A fusion of like parts in the "feet" of many rhizopods has 

 also been repeatedly observed and described. 



As far as we know, only simple contact is needed for 

 this fusion, besides the required degree of homogenity. 

 We may, therefore, regard it as a mechanical process and 

 use it as an element in the explanation of normal cell- 

 division. In Spirogyra it evidently accomplishes the fu- 

 sion of the spindle with the inward growing ring, and 

 later determines the final closing up of the opening that 

 was left in the ring. 



4. The Regeneration of Protoplasts after Wounding 



Even though, in the normal course of development, 

 the individual organs of a cell multiply by division, this 

 does not necessarily imply that this rule must be without 

 exception, and that there cannot be cases where nature 

 tries to achieve its ends in another way. Especially where, 

 through outward interference, such as wounding and mu- 

 tilations, individual members of a protoplast are com- 

 pletely lost, it might be expected that a regeneration in 

 another way might be possible. 



To be sure observations now available do not warrant 

 the assumption that such cases actually occur. But this 

 does not, by any means, exclude their possibility. And 

 on this possibility I want to lay great stress in this con- 

 nection, for the hypothesis of intracellular pangenesis 



