458 BOTANICAL GAZETTE [December 



er of the male gametes continues for almost 

 le female gametes is comparatively short, t 

 swimming condition observed having bee] 

 test <c minutes. Toward the end of the 



motile 



male and female erametes, the movements 



and then cilia are no longer recognizable, seemingly being withdrawn 

 or coalescing with part of the plasma membrane of the gamete body, 

 and finally the shape of the body becomes spherical. However, 

 in a number of cases gametes caught in the thallus of algae while 

 swimming between the slide and cover-glass remained active for 

 more than 24 hours, and then became spherical; when stained at 

 that time they showed the cilia still persisting and not coalescent 

 . with the plasma membrane. 



The union of male and female gametes and the subsequent 

 nuclear behavior were studied in material from artificial cultures. 

 A number of dishes were prepared containing either male or female 

 plants bearing mature gametangia. When the discharge of 

 gametes became abundant, the sea water of the dish containing 

 thousands of swarming male gametes was added to a dish contain- 

 ing vigorous female gametes. Then part of this mixture was 

 observed under the microscope in living condition and part was 

 fixed every 30 minutes for 24 hours, and then at 26, 28, 32, and 48 

 hours, and later, every 3 or 5 days up to 75 days. The following 

 description is based upon material obtained in this way. 



The male gametes while swimming freely become attached to the 

 female gametes which are either sluggishly swimming or have come 

 to rest, but have not yet formed a cell wall. When the male gamete 

 becomes quiescent, before coining in contact with the female 

 gamete it withdraws its cilia and its shape becomes spherical. 

 The nucleus is full of chromatin which is clearly broken into 24 

 independent chromosomes. The nuclear membrane is very- deli- 



cate (fig. 94) . When a male gamete 



female 



ery 



95) 



Then the plasma membranes which 

 the male and female gametes become 



