32 PROTOPLASMIC THEORY BEFORE 1860 NAEGELI. 



and Schwann say, and does not originate by any chemical 

 action of one kind of substance upon another, but is an organic 

 process in fact a secretion (128). Likewise " the membrane 

 bears no immediate share in the production of the new cell, it 

 is merely the contents of the parent cell that here come into 

 consideration" (138). The young cell first appears as a layer of 

 mucilage surrounding a nucleus. Then a membrane becomes 

 visible on the surface of the mucilage. Then as the cell ex- 

 pands there is a hollow in the interior, and the mucilage remains 

 on the wall as a thin layer. This layer is what Mohl has named 

 the primordial utricle. It is thicker at the place where the 

 nucleus lies, and the latter is often imbedded in it : and it was 

 this circumstance no doubt which made Schleiden think that it 

 lay between the two layers of the cell wall, which cannot be, as 

 Naegeli has seen the nucleus become detached (111). This 

 " mucilaginous layer (primordial utricle) is always present in 

 cells as long as they retain their vitality," and "it secretes 

 organic unazotized molecules which form the new thickening 

 layers " [of the ceil wall] (124). " These facts prove that organic 

 unazotized molecules are secreted on the surface of living vege- 

 table mucilage, and these enclose the mucilage in the form of a 

 membranous liyer" (124). It is here explained in a note that 

 this "mucilage" corresponds to the " protoplasma " of Mohl. 

 With respect to the nucleus his views are very complicated and 

 not very satisfactory even to himself, but its chief function is 

 the " individualization of the cell contents." In the process of 

 cell multiplication " a nucleus is formed, and this nucleus indi- 

 vidualizes a portion of the contents by attraction," and there- 

 fore the formation of the new cell takes place as above de- 

 scribed. However, in many organisms, e.g., chlorococcus, Hoema- 

 tococcus, the germ cells of fungi and lichens, &c., the nucleus 

 may be wanting in the whole process of cell-multiplication 

 (132). 



He contests Meyer's view that cells might originate in the 

 homogeneous mixture produced by dissolved matters ; and also 

 that of Mirbel, who said the same of the cambium of the root 

 of the date palm. He also says Endlicher and Meyer are wrong 

 in saying that cells originated in inter-cellular substance. He 



