142 SEX IN MICROORGANISMS 



"zygospore" was not followed. He called the process "copulation." 

 Entz (1907) found similar stages of this species in preserved material 

 from "Balaton-Sees." Hall (1925) interpreted binucleate cysts of this 

 species as possibly indicating previous cell fusion. 



Perhaps the most interesting reports for this group are those of 

 Diwald (1938) for Glenodinium hibiniensifomie. The life history 

 includes the following: binary fission, with parent shells separating 

 along the girdle; formation of two vegetative "swarmers" inside the 

 parent shell; encystment followed by excystment and binary fission; 

 sexual reproduction with the following stages: (a) two successive 

 divisions inside the parent shell forming four gametes (Fig. D, 1 to 4) 

 which are released from the shell (5); (b) fusion of isogametes to 

 produce zygotes (6 to 8); (c) encystment of the zygotes (9); (d) 

 excystment of zygotes after at least 10 days' rest (10); (e) while still 

 immobile, and surrounded by a jelly-like covering, two successive 

 divisions to produce "swarmers" (11 to 13); (f) development of 

 flagella and resumption of vegetative hfe (14). Diwald believed that 

 meiosis took place during the two divisions following excystment of 

 the zygotes, but chromosomes counts were not given. He found that 

 gametes did not form for a certain time after excystment. Further- 



TABLE I 



Results of Mixing Gametes of 16 Clones of Glenodinium luhiniensiforme 



IN All Combinations 



"Copulation" indicated by -(-; no union indicated by — . (From Diwald, 1938) 



