n] 



THE BEACH AND ROCKS 



23 



impossible. This is the phase commonly known and 

 recognised as the plant, which by growth and repeated 

 division of its cells may attain large size. The other 

 phase is one of freedom and active movement. The 



Fig. 3. Ulothrix zonata. Showing production of gametes. A 

 filament from which the gametes (sexual cells) are escaping. 

 J5 = a gamete. C, D = conjugation of gametes, in pairs. E = 

 zygospore. F=zygote, or result of fusion. G = germs produced 

 from it. H"=a filament with germinating zoospores (z). 

 A, H, F and G x 200. B E x 333. (After Klebs.) 



protoplasm after division escapes from the restricting 

 cell-wall in the form of zooids, each capable of inde- 

 pendent movement in the water into which they 

 escape. From their minute size and their dependence 

 upon suitable external conditions for their escape and 



