UTRICULAR STRUCTURES. 189 



The distinction between the two is more difficult to 

 find, especially because the origin of the utricle is not yet 

 sufficiently made out. I believe, however, that even with 

 our present knowledge, the distinction may be at least so 

 far established, that cell and utricle appear as absolute, 

 distinct conceptions. The comparison may take into 

 consideration either the relation of the two structures to 

 the individual plant, or the two structures independently 

 of general relations. 



In reference to the relation to the vegetable organism, 

 cell and utricle exhibit the following distinction. The 

 cell is the elementary organ, which takes part immediately 

 in the formation of a tissue. The plant first becomes 

 independent with the cell. It developes through the 

 formation and growth of cells ; it lives through the cells. 

 The utricle, on the other hand, is an elementary organ 

 which takes part only mediately in the origin, structure, 

 and life of the plant, because the utricle is merely a part 

 of the cell. Consequently we may call the cell the imme- 

 diate, the utricle the mediate elementary organ of the plant. 



Considering cell and utricle independently, as indivi- 

 dual organisms, we can at present establish merely the 

 following distinction. The cell needs for its production 

 a nucleus, formed previously ; it is formed around a 

 portion of organic cell-contents in which a nucleus is 

 inclosed.* The utricles, on the contrary, never originate 

 around a nucleus, only the nuclear utricles originate 

 around a nucleolus. We may accordingly define the 

 cell and the utricle in the following terms : 



The cell is an individual quantity of contents, inclosed 

 by a homogeneous membrane, and individualized through 

 the influence of a nuclear utricle ; it is the immediate 

 elementary organ of the vegetable organism. 



The utricle is an individual quantity of contents, in- 



* I have shown, in the preceding Essay, that in the first place a nucleus 

 is produced which individualizes a greater or smaller quantity of the sur- 

 rounding contents, through attraction, and that this individualized portion 

 of contents acquires a membranous coat upon its surface. 



