CELL-FORMATION. 125 



a membrane makes no difference as to its function. Even 

 in regard to the secreted layer, the distinction is not 

 essential, and exists only in so far that in the one case 

 this is called a membrane, in the other a layer of thicken- 

 ing. That there is no distinction between membrane and 

 thickening layer is proved by the formation of membrane 

 on the surface of a partially free mucilaginous layer, in 

 the cells of Algae. There the newly-formed piece of mem- 

 brane passes continuously into the innermost layer of 

 thickening ; or, in other words, the gelatinous deposit 

 secreted simultaneously over the whole surface of the 

 mucilaginous layer, appears in some places as a layer of 

 thickening, in others as a membrane. 



If we conclude from the fact that the mucilage pro- 

 duces membrane or layers of thickening through secretion 

 on its external surface, and that there is no essential dis- 

 tinction between them from the formation of membrane 

 to that of cells, it follows logically that the membrane must 

 originate through secretion from the mucilage in all cell- 

 formation. This conclusion is very strongly supported 

 by certain phenomena in cell-formation itself. 



proteine-compounds. An agreement between these views would not be 

 readily effected. In addition there is a substance which is called schleim by 

 both parties ; this is the homogeneous, thickish, colourless matter, forming 

 the total contents of the young cell, and the homogeneous, denseish, colourless 

 ingredient in the contents of old cells. If, now, schleim is to have the sig- 

 nification of one or other (ternary or quaternary) of the chemical substances, 

 it is incorrect to call the last-mentioned schleim. Eor this is certainly not a 

 pure substance, but at the least a mixture of ternary (gum and sugar) and 

 quaternary substances (proteine-compounds). This mixed matter is of the 

 greatest importance in the life of the cell, since it is effective in cell-forma- 

 tion, in the first instance fills the whole cavity of the cell, subsequently lies 

 upon the wall as mucilaginous layer, and traverses the cavity in currents 

 of circulation, lastly, forms the contents of many utricles. (See the 

 Essay ' On the Utricular Structures' in this volume.) It therefore requires 

 a special name, and since the term schleim, on the one side, may certainly be 

 spared from the nomenclature of ternary and quaternary organic matters, 

 while on the other it is already in use in the proposed sense, it would be 

 most advantageous to name the homogeneous denseish substance of the 

 vegetable cell-contents, composed of mingled ternary and quaternary matters 

 schleim. [Mohl has proposed, and Schleiden and others have adopted, a 

 better name, protoplasma, which has solely a physiological value, confusion 

 resulting from the misuse of a term having a chemical signification. A. H.] 



