II] 



THE BEACH AND ROCKS 



21 



larger numbers in each parent-cell. In size they 

 resemble the third type, which are the sexual zooids, 



Fig. 2. Ulothrix zonata, showing formation of zoospores. A- A 

 filament in the vegetative condition, B = a, filament whose cells 

 are producing zoospores. C = a single zoospore. JD = a zoospore 

 coming to rest: o = eye-spot: c = pulsating vacuole. ^ = germi- 

 natmg zoospores. F=micro-zoospore. G 1 — 3 = germinating 

 microspores. A,Bx200. C— G 1, 2 x 333. (? 3 x 166. (After 

 Klebs.) 



or gametes ; but these are readily distinguished from 

 them by the number of their cilia, which are two in 



