Development, and Structure of the Vegetable Cell. 33 



side of the original cell-nucleus, arranged in correspondence 

 with the transverse diameter of the joint-cell. In the next 

 stages of development they take up a position in accordance 

 with the longitudinal axis of the cell within the nuclear cell, 

 which has now become globular. A glance at figs, 81 & 83-85 

 will render this condition quite clear. These are nuclear cells 

 of Spirogyra nitida, Kg., such as often occur in cultivated ex- 

 amples of this species, with their membranes distended by the 

 action of water containing carbonic acid. 



Fig. 84 shows ver>' distinctly that the new cell-nuclei, which 

 here contain no nucleoli, are enveloped by the outer membrane 

 of the cell-system produced by the development of the cell- 

 nucleus. 



In fig. 85 these two new cells (the daughter cells of the entire 

 cell-system) are still more expanded within their mother cell, so 

 that they surround the nuclear cell lying between them, and 

 enclose it with their contiguous membranes (as also in fig. 81). 



The nuclear cell, however, still exists uninjured between 

 them, as in fig. 81- (and fig. 83 shows another similar state of 

 development seen from the side), although its absorption now 

 generally begins, and at the same time a secondary cell is pro- 

 duced in each of the daughter cells. The daughter cells, dis- 

 tended by carbonic-acid water, here represented contain as yet 

 no cellular structures, such as are ordinarily present in norm- 

 ally developed cells at this stage of development. 



In fig. 81 a normal case is represented; a cell-nucleus is 

 situated in the daughter cell on the wall directed towards the 

 centre of the new joint-cell, as is the rule in Spiroffyra, and 

 therefore on the side opposite to the original cell-nucleus. 



This cell-nucleus of the young daughter cell usually appears, 

 in its earliest grades of development, in the form of a spherical 

 accumulation of mucilage. In this mucilage, however, in other 

 eases, a vesicle may be seen imbedded, and, a little later, one or 

 rarely several nucleoli may be detected. 



That the external membrane of the cell-nucleus (which, as 

 already stated, is frequently seen, in some Spirogyra, to be com- 

 posed of several endogenous cells, and therefore developed into 

 a complete cell-system) may attain, just as in (Edogonium, to 

 the full size of the mother cell is shown by states such as that 

 represented in fig. 80, which are met with occasionally, although 

 rarely, in cultivated plants of Spirogyra. (Fig. 80 is drawn 

 from a specimen which had lain for some time in carbonic-acid 

 water ; and this certainly assisted somewhat in the distention of 

 the cell-membrane, as it also caused the primary membrane of 

 the ioint-cell to become particularly prominent.) 



Not unfrequently, in a disproportionately long cell, two cell- 

 Am.i^ Mag. N. Hist. Ser.3. Fo/.xiv. 3 



