CHYTRIDIALES 413 



which the shape of the mass changes, eventually escaping singly; 

 resting spore not observed. 



Saprophytic in exuviae of midges and mayflies, Sparrow (1937a: 41, 

 pi. 2, figs. 1-5), United States. 



This species is based on a fungus originally referred to Rhizidium 

 mycophilum (Sparrow, be. cit.). The identity of the British material 

 originally discussed under the latter species (Sparrow, 1937a) is open to 

 question and, hence, it is not included. 



A remarkable swarming period is undergone by the zoospores after 

 discharge. A few moments after the zoospores emerge they assume 

 individual movement; the rounded mass then moves away from the 

 immediate vicinity of the sporangium and becomes reniform. During 

 the violent swarming that continues, the shape of the mass changes to 

 broadly sagittate. Eventually, individuals escape by way of the two 

 apices of the lobes of the "arrowhead." The method of escape and a 

 boundary line of bacteria around the mass strongly indicates that a 

 definite vesicle surrounds the zoospores. 



Rhizidium vorax (Strasburger) Sparrow 

 Aquatic Phycomycetes, p. 279. 1943 



Chytridium vorax Strasburger, Jenaische Zeitschr. f. Nat., 12: 564. 1878. 

 Rhizophlyctis vorax (Strasburger) Fischer, Rabenhorst. Kryptogamen-FL, 

 1 (4): 120. 1892. 



Sporangium spherical or nearly so, mostly about 40 \x in diameter, 

 wall thin, smooth, colorless, with a short lateral discharge papilla; 

 rhizoids extensive, branched, stout, strongly polyphagous, attacking as 

 many as from thirty to forty host cells, arising from a broad main axis 

 attached to the base of the sporangium; zoospores spherical, 6.6 \i in 

 diameter, with a relatively large colorless basal globule, an anterior 

 visible nucleus, and a flagellum, after discharge remaining for a time 

 undergoing amoeboid changes of shape before rounding off and 

 swimming away, movement swimming or amoeboid ; resting spore not 

 observed. 



Parasitic on Sphaerella (Haematococcus) lacustris, occasionally attack- 

 ing resting individuals of Chilomonas and other swarmers, Germany. 



