GROWTH OF CELLS. 153 



and the cavity is filled with colourless fluid, and comes 

 into communication with the transparent cavity of the 

 original cell. 



The apical growth consequently commences with the new 

 formation of homogeneous mucilage, which produces new 

 membrane, and is continued by the persistence in new for- 

 mation of membrane-forming mucilage. 



The question now comes, what is the relation of the 

 apical growth to universal growth and to cell-formation ? 

 The relation may be conceived in two ways : 1st, in 

 reference to the contents; 2dly, in reference to the mem- 

 brane. I will here, as in the universal growth, only enter 

 upon the latter point. 



Schleiden and Schwann have strictly discriminated two 

 epochs in the development of the cell, namely, the origin 

 of the membrane, and its growth. This distinction, how- 

 ever, according to the view of cell-formation above estab- 

 lished, is certainly not so great as it appears in Schleiden 's 

 and in Schwann's theory. According to this theory, the 

 material for the original production of the membrane is 

 merely furnished by the mother-liquor, from which it 

 crystallizes ; the material for the growth of the membrane 

 is, on the contrary, partly or wholly furnished by the cell- 

 contents ; it is, namely, deposited from the contents, or 

 acquired by the endosmose and exosmose through the 

 membrane. 



According to my theory of cell-formation, the original 

 production and the growth of the membrane have the 

 same material cause. For both purposes, organic matter 

 (in plants mostly gelatine) is secreted from the contents. 

 Origin and growth are, in the same way, a product of the 

 contents. They merely differ from each other relatively. 

 The original production of membrane gradually changes 

 into growth of membrane. A line of demarcation be- 

 tween them is quite arbitrary. 



We see, therefore, that in this point the membrane 

 behaves just like every other organism. In none, cer- 

 tainly, does there exist a strict and absolute boundary 



