ZOOSPORES 



219 



cilia, one directed forwards and the other backwards during 

 movement, and these are attached to one side adjacent to the 

 chloroplast and the prominent eye-spot (Fig, 119, g). 



The production of zoospores serves as a rapid means of 



FIG. 119. Ectocarpus. a, small part of a thread showing a gametangium 

 (g.), liberating gametes ; b, tip of a branch showing hair-like termi- 

 nations ; c, small part of a thread bearing a zoosporangium (s.) ; 



d, part of thread showing cell-contents and chloroplasts (ch.) ; 



e, branched filament bearing several gametangia (g.) ; f, plant of 

 E. littoralis, natural size ; g, zoospore ; h and i, stages in fusion of 

 gametes ; k, zygospore, still showing two chloroplasts and two eye- 

 spots, (a, after Thuret ; 6 and d-f after Migula ; c and g after Reinke ; 

 h-k after Berthold.) 



multiplication and dispersal at times when vegetative activity 

 is at its height, but this method lacks the stimulus which sexual 

 fusion appears to provide. As a matter of fact continued 

 asexual .reproduction has, in certain cases (e.g. some Diatoms), 



