396 THE MICROSCOPIST. 



row ; apex of sac opens by circumcision, and the gonidia 

 grow out into tubes like the parent in an umbel, their 

 stipes remaining inserted ; each new tube repeats this to 

 fourth or more generation, the last generation from the 

 compound umbel emitting its gonidia as two-ciliated zoo- 

 spores. 



21. Chytridium. Parasitic ; minute globular pyriform 

 or urceolate sac, attached by a foot which penetrates into 

 the supporting body (mostly a Confervoid) ; cell-contents 

 colorless, becoming two-ciliated zoospores, escaping by 

 dehiscence of a valvelike lid, or by simple rupture of sac. 



22. Pythium. Parasitic ; a globular sac in the interior 

 of cell of diseased Confervoids, often in groups ; contents 

 colorless ; sac grows to flasklike form, the neck perforat- 

 ing the wall of the nurse-plant and bursting to emit ac- 

 tive gonidia (?). 



12. VOLVOCINE^E. Microscopic, cellular; fresh-water 

 groups of bodies, like zoospores, connected into four by 

 enveloping membranes ; either assemblages of coated zoo- 

 spores by cohering membranes, or of naked zoospores in 

 a common membrane; the zoospore-like two-ciliated bodies 

 perforate the coat, and by conjoined action move the entire 

 group; reproduce by division (Gonium)^ or by single cells 

 becoming families (Pandorina, Volvoz), and, by resting 

 spores, formed after impregnation of some cells by sperma- 

 tozoids formed from contents of other cells. 



Solitary : 



No cilia, Gyges. 



A pair of cilia, PROTOCOCCUS. 



Grouped : 



Square layer, gonidia of 2 cilia, GONIUM. 



