178 THE BEGINNINGS OF LIFE. 



of the wall, retreat from this membrane, and present 

 themselves as a new, everywhere free cell, destined for 

 reproduction. The cell-body thus detached from the 

 walls, appearing in a new form, with a new vital direc- 

 tion, presents itself with regular form and boundaries, 

 before a trace of the cell membrane subsequently cloth- 

 ing it is visible. It mostly assumes a perfectly globu- 

 lar form, even when the mother-cell is longish ; in this 

 first period of formation its surface appears somewhat 

 uneven from the projection of chlorophyll vesicles; the 

 whole internal cavity is filled up, and of deep green 

 colour. Very slowly and gradually there appears, first 

 a simple, afterwards a double, and sometimes even a 

 triple-layered membrane upon the surface, while the 

 chlorophyll and starch formations in the contents pro- 

 gressively vanish, and give place to reddish oil-drops, 

 which at length occupy nearly the whole cavity, and 

 give the seed-cell a brownish-red, sometimes even a 

 red-lead coloured appearance 1 . The seed-cells of the 



1 These metabolic changes of a chemical nature taking place within 

 the cell are of the highest interest. We have already had occa- 

 sion (note, p. 105) to refer to the properties conferred upon a seed by the 

 presence of much oil and starch in its interior, and we shall subsequently 

 (p. 712) have occasion to refer to the metabolic capacities of fatty 

 products. One of the best instances of the conversion of chlorophyll 

 and protoplasm into colourless fatty and other materials, and of the subse- 

 quent reconversion of these into coloured protoplasm, is to be met with 

 in the life-history of Palmoglea. The reproduction of this plant is 

 brought about by the union of two green vegetative cells, the con- 

 tents of which are converted into a single seed- cell. Braun says : 

 ' During the gradual growing together and fusion of the two combining 

 cells, we may trace the formation of fixed oil step by step. Before the 



