12 



SEX AND HEREDITY 



It is not quite so simple in structure as those before des- 

 cribed, for it consists of a number of encysted cells 



s 



FIG. 6. 



Ulothrix zonata. A, young filament attached by rhizoid, r ( x 300) ; B, portion 

 of filament with escaping swarm-spores ; C = single swarm-spore ; Z) = formation 

 and escape of gametes ; E gametes ; F, G = conjugation of gametes ; #=zygote; 

 / = zygote after period of rest ; K = zygote after division into swarm-spores. 

 (After Dodel-Port. From Strasburger. B-K x 482.) 



attached end to end, and sharing a common life. It is 

 thus a Plant with a multicellular body, which is fixed at 

 its base to the substratum (Fig. 6). In this state the 

 plant leads a vegetative existence, its cells nourishing 



