163 THE PHENOMENON OF 



each cell of the filament. The birth of these is effected 

 by an extremely regular bursting of the parent-cell in the 

 direction of a transverse annular fold, occurring near the 

 anterior end of the cell, so that the cell opens as it were 

 by a hd, the detached upper portion often remaining 

 fixed at one side, and opening only laterally, the result of 

 which is of course a knee-like bending, when the opening 

 cell lies in the middle of the filament. The cell-contents 

 previously lying closely appHed upon the cell-wall, and 

 merely betraying the impending birth by their darker 

 colour, are then very gradually extruded through the 

 opening of the box-like cell, exhibiting, even during 

 the movement, at the posterior end lifted up from the 

 bottom of the cell, a brighter spot, which after the birth 

 becomes more distinctly developed as the nipple-shaped, 

 hyaline apex, bearing the wreath of cilia. During the 

 birth the germ-cell is here also preceded by an extremely 

 delicate vesicle, which gradually expands into a large sac, 

 the posterior end of which, however, never leaves the 

 mother-cell. This sac is often not torn through for 

 several minutes, but then it sets free the swarm-cell, 

 already revolving while inside, which darts away from it 

 like an arrow. The vesicle is here neither more nor less 

 than the innermost layer of the mother-cell, still soft, 

 taking no share in the dehiscence of the mother-cell, and 

 expanding by the absorption of water. It is coloured 

 distinctly blue by the application of tincture of iodine, 

 even without previous treatment with sulphuric acid. 

 That the germ-cell set free from its prison in the 

 manner described, does not yet possess a cell-membrane, 

 but represents merely the mass of contents of the mother- 

 cell, is testified, as in Vaucheria, by its want of cohesion. 

 I once saw, in CEdogonium apophysatum a small torn-ofF 

 piece of the cell-contents left behind and assume the 

 shape of a separate globule, which did not arrive at 

 birth and movement, but remained in the cell. Probably 

 the original cause of the tearing in this case was a slight 

 adhesion of the cell-contents to the cell- walls, at a small 



