366 Mr. A. Henfrey on the Development of Vegetable Cells. 



M. Miiller, in his researches upon the development of Char a *, 

 declares that cell-formation is effected by two different and ap- 

 parently very distinct processes. 



Some of the cells, he says, are produced from cytoblasts in the 

 manner described by Schleiden, from whom, however, he differs 

 in some respects, since he regards the membrane developed from 

 the cytoblast as identical with Mohl's primordial utricle, and 

 therefore not as the permanent cell-wall. 



In other cells multiplication takes place by division, and the 

 figures in which he represents the condition of the primordial 

 utricle in various stages of its division, agree perfectly with the 

 appearances observed by Prof. Mohl and myself. 



With respect to the production of cells from cytoblasts, I do 

 not think the evidence he has offered conclusive ; one of his 

 figures indeed, which he owns that he cannot explain, rather in- 

 clines me to believe, not that the cytoblasts are the efficient 

 causes of the development of new cells, but that their presence 

 in certain cases of multiplication of cells by division, has led 

 Miiller, like Schleiden and others, to a misconception of their 

 function. 



I will not venture an opinion as to the real function of the 

 cytoblast, but this much I may state, that it is generally present 

 at a very early period of cell-life, and usually of the full size. 

 Now cell-division often takes place, or rather commences at an 

 epoch when the cytoblast completely fills that portion of the pri- 

 mordial utricle which is about to form a new cell ; on the subse- 

 quent expansion of the utricle its walls retreat from the periphery 

 of the cytoblast or nucleus which then remains suspended in the 

 cavity or attached to the wall. This may be observed in the 

 moniliform hairs of Tradescantia. 



It is evident that we have here an appearance similating the 

 development of membrane from a cytoblast as described by 

 Schleiden ; and since I have never been able to see the produc- 

 tion of cytoblasts themselves by the aggregation of the granules 

 of the mucilage, I think it most probable that it has been a mis- 

 interpretation of similar phenomena which has given rise to 

 Schleiden's theory. 



Miiller has represented a cytoblast or nucleus cut into two 

 portions by the fold of the primordial utricle. 



The same division of the perfect nucleus by the septum of the 

 cell has been observed by Unger. This is a different thing from 

 the original division of the nuclei which is said to occur at the 

 earliest epoch of the life of the cell, but it is direct evidence 

 against the assumption that the cytoblast is the active agent in 

 the production of the new membrane. 



* See Ann. Nat. Hist. vol. xvii. p. 254, &c. 



