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 = & filament whose cells 

 are producing zoospores. (7 = a single zoospore. D = a zoospore 

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

 nating zoospores. F^micro-zoospore. G 1 3 = germinating 

 microspores. A, J5 x 200. C G 1, 2 x 333. G 3 x 166. (After 

 Klebs.) 



or gametes ; but these are readily distinguished from 

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



