40 



PROTISTS AND DISEASE 



germinates in water by developing a hypha. In some 

 kindred genera, e.g. Cystopus, Fig. 8, g, the oospore pushes 

 out a process which becomes a zoosporangium. 



Nuclear Processes in Pythium. The nuclear changes 

 in the sexual process of Pyihium,, Fig. 7, have been studied 

 by A. H. Trow, and by Kiichi Miyake (1901). Young 

 oogonia measure from 20/x to 25/a,, their nuclei are larger 



FIG. 7. NUCLEAR PROCESSES IN PYTHIUM DEBARYANUM. a, young 

 oogonium ; b, nuclear divisions in both oogonium and antheridium ; 

 c, early anaphase, from oogonium ; d, one nucleus in each game- 

 tangium is intact, the rest disintegrating ; e, passage of male nucleus 

 into oosphere ; /, ripe oospore with membrane and end of empty 

 antheridium. After Miyake, reduced to ?. 



than those of the hyphae. When the ovum is nearly mature 

 its nuclei divide by karyokinesis, and all save one move to 

 the membrane and disintegrate, d. The spindle is intra- 

 nuclear. Eight chromosomes were counted ; the author 

 could not detect a reduction. The remaining nucleus lies 

 in the middle of the ovum. Events in the antheridium are 

 similar to those in the oogonium. 



Near the single remaining nucleus of the oosphere 

 A. H. Trow observed the formation of a, coenocentre in 

 P. ultimum. 



