CELLS AND THE ORGANISM 45 



to make up the Cladophora plant. It may 

 easily be shown that the co-ordination is 

 a real one, and that it depends in some way 

 on the mutual reactions between one cell and 

 another, by means of an experiment on one 

 of the marine species of the genus. If the 



Fig. 6. Cladophora sp. I. General habit. II. Magnified 

 filament. 



plant be placed in sea-water to which a 

 strong salt solution is slowly added (up to 

 about 12*5 %), the protoplasm of each of 

 the cells contracts away from the walls, and 

 forms an ellipsoidal mass within each cell 

 cavity. The protoplasts then surround them- 

 selves with new walls. After allowing them to 



