CELL-FORMATION. 129 



by a membrane ; the other is where the contents of a 

 cell become detached from the walls only in places, and 

 produce new membrane on these places. One extreme 

 is a perfect cell-formation ; the other merely a slight 

 alteration of the form of the cell, combined with a partial 

 production of new membrane. One extreme is the pro- 

 duction of a new individual cell ; the other is the re- 

 organization of the partially injured individuality. 



Between the two extremes occur a quantity of inter- 

 mediate stages, in which it is doubtful, in particular 

 cases, whether the old cell persists in an altered form, or 

 whether a new cell has replaced it. The fact is certain, 

 but the explanation is furnished by the observer. In all 

 those cases where the mucilaginous layer is merely de- 

 tached in places from the cell-wall, and produces pieces 

 of membrane, we always recognize the cell as the same, 

 with partially altered form and membrane. In all those 

 where portions of the contents become isolated, and 

 complete their separation from one another by the forma- 

 tion of membrane, we suppose new cells to take the place 

 of the parent-cell ; but if the entire contents of a cell are 

 detached from the wall, become isolated, and then form 

 a new complete membrane, we may call this a cell-forma- 

 tion, as well as we can call it formation of membrane. 

 The contents of the old and new cell are exactly the same, 

 the walls altogether different. Is a new individual 

 formed, or is the individual merely reorganized (through 

 regeneration of an organ) ? This case stands just mid- 

 way, and admits either explanation equally well. A step 

 toward one side (if not the whole contents, but merely a 

 portion, become detached from the wall), or one step 

 toward the other (if not the whole contents, but merely 

 a portion of them become completely isolated), will strictly 

 decide the explanation to be either reorganization of the 

 cell, or cell-formation. 



The transition occurs again in a different way. If the 

 contents of a cell become detached from the wall in one 

 place, and acquire a new coat of membrane over this 



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