THE CELL 107 



cial cells unite to form the spore that produces the new 

 cell. 



"When these cells formed by internal division escape 

 from the mother cell into the water, it is discovered that 

 they are able to swim about by the lashing movements of 

 four cilia, that appear in a cluster at the pointed end. 



"A special cell thus set apart for reproduction is called 

 a spore, and spores that swim are distinguished as swim- 

 ming spores. A very important fact about ulothrix there- 

 fore is that it reproduces not only by vegetable multipli- 

 cation but also by swimming spores. 



"In other cells of the same filaments, or in cells of fila- 

 ments under different conditions, the same formation of 

 cells by internal division may be observed, but the con- 

 tained cells are smaller and more numerous. When they 

 escape it is discovered that they also are ciliated swim- 

 ming cells but since they do not produce new filaments, 

 it is evident that they are not swimming spores." 



I think I have now covered in a general way the most 

 important features connected with the inner life of the 

 cell. I might mention that the ability of the cell to pro- 

 vide itself and build around itself protective coverings and 

 armor of different materials and designs, from a soft flexi- 

 ble covering to one as hard as flint, has been the stepping 

 stone by which the cell has been able to build the many 

 peculiar structures, and to display the marvelous archi- 

 tecture which we shall find when we come to consider 

 the living structures, in a chapter devoted entirely to that 

 subject. 



