1:20 VEGETABLE CELLS. 



I have already remarked* that, in the abnormal cell- 

 formation in the cells of Alga?, a great multiplicity of 

 conditions occur in regard to the contents which produce 

 the membrane, and that a continuous series of gradations 

 exists from abnormal cell-formation to the normal phe- 

 nomena of cell-life. Sometimes a free cell is formed by 

 a small portion of homogeneous mucilage, sometimes by 

 a larger quantity of mucilage containing chlorophyll and 

 starch ; sometimes a considerable portion of the cell- 

 contents produce, here a membrane, there layers of thick- 

 ening ; sometimes the whole contents form either a 

 perfect membrane, or partly membrane, partly thickening 

 layer, or a complete layer of thickening. These various 

 phenomena are all connected by a number of intermediate 

 states, so that the necessary cause and nature must be 

 alike in all. 



Since now, in some cases (if, namely, the mucilage 

 borders on an existing membrane or on water) it is cer- 

 tain that the membrane cannot originate in any other 

 way but through secretion from the mucilage, which is 

 afterwards inclosed, we must undoubtedly assume a like 

 origin in the other cases, where a part or the whole of the 

 surface of the mucilage is bounded by fluid, unazotized 

 or azotized contents. Consequently, in free abnormal 

 cell-formation, the membrane is formed through secretion 

 from the portion of contents which becomes a cell, and 

 by no means in any other way from the rest of the 

 contents of the parent-cell. 



Passing from the abnormal parietal and free cell- 

 formation to the normal parietal cell-formation, we find 

 here also that the phenomena themselves lead to that 

 assumption through a conclusion deduced from analogy. 

 I have already discussed this at length in the section on 

 parietal cell-formation. The contents of the parent-cell 

 divide into one or more portions. The new membrane 

 originates in some places between the mucilaginous con- 



* Pages 97, 99, 114. 



