CELLS AND THE ORGANISM 47 



instances connecting strands of protoplasm 

 have been demonstrated, and these serve as 

 the obvious channels of direct communication 

 between the living contents of adjacent cells. 

 When the interchange has been sufficiently 

 interrupted the old order cannot be again 

 restored. The cells are released, as it were, 

 from the influence that previously controlled 

 them and caused them to be welded together 

 into a higher individuality. Each cell, thus 

 breaking away from the union, reverts to 

 a more primitive condition, recovering an 

 independence akin to, and perhaps identical 

 with, that which distinguishes zoospores 

 and other reproductive cells that are set 

 free from the organism which gives them 

 birth. 



Although the simpler filamentous algae, 

 and especially the branching kinds, share with 

 the primitive flattened leaf-like types the 

 advantage of disposing their surfaces so as 

 to make the most of the means of illumin- 

 ation, they yet remain far behind the more 

 advanced types, in which other functions 

 beside those of photosynthesis press for 

 notice. 



The larger seaweeds, although their green 

 colour is masked by yellow or red pigment, 

 are as dependent on light for the manu- 

 facture of their food as are their simpler 

 green companions. But their size introduces 

 an element of physiological complexity. 



It will be remembered that it is only the 



