10 Prof. H. Karsten on some Phenomena of 



joint-cells of S. nitida it is most decidedly seen that the new 

 partition-walls are not produced by a fold of the membrane of 

 the parent cell ; for the several chlorophyll-laminse or bands 

 which are present, and completely coherent or continuous at 

 first, overlie the septum which originates from the mutual ap- 

 position of the endogenous cells (fig. 13). 



In fig. 15, a cell of S. orthospira is represented, in which the 

 two daughter cells, a, a (covered by slender chlorophyll-vesicles, 

 within the secondary cell b, which has been cautiously detached 

 by diosmosis from the primary cell, by the addition of a weak 

 solution of chloride of calcium), are in process of forming a new 

 septum between themselves, and having the nuclear cell inter- 

 posed. The formation of folds from the secondary cell (primor- 

 dial sac) is evidently here not the cause of the septum in exist- 

 ence, though it be still incomplete with reference to the parent 

 cell. 



Fig. 16 exhibits the following stage of development of a joint- 

 cell of the same individual, in which neither the two daughter 

 cells nor the secondary cells could be detached by the same 

 reagent from the wall of the mother cell, although the secondary 

 cells of the daughter cells have become separated from the coats 

 of their primary cells. These latter formed the still extremely 

 delicate septum which divides the cavity of the mother cell into 

 two portions. The secretory materials (chlorophyll, starch, &c.) 

 are in this stage already enclosed within the secondary cells of 

 the daughter cells, whilst in the previous phase, represented in 

 fig. 15, they are still found within the secondary cells of the 

 parent cell. 



The process of absorption of the chlorophyll-vesicles contained 

 within the mother cell, and their reproduction in the daughter 

 cells, may be detected in this genus of plants, although not in 

 its details ; but in (Edogonium I have witnessed this process after 

 the origin of new joint-cells. 



These at first exceedingly delicate partition-walls, developed 

 in a normal manner, can scarcely be confounded with the cen- 

 tripetal circular folds which the cell-membrane of badly nou- 

 rished Confervse, particularly Cladophora and SpirogyrcE, not un- 

 frequently produce ; for these latter are much thicker, and their 

 central edge always rounded, as is shown in figs. 12 & 14. In 

 these examples, the membrane of the secondary cell which was 

 detached from the thickened wall of the primary, as a result of 

 diosmosis, at the constricted part at x, and which, during the 

 operation of the reagent, was disturbed from its position, was 

 free from chlorophyll. This nitrogenous secretory matter could 

 not, from the deficiency of suitable nutritive material, develope 

 itself proportionately with the growing cell-membrane, and. 



