980 AQUATIC PHYCOMYCETES 



delimited within the sporangium, at discharge the first few zoospores 

 forming an amorphous subspherical mass in a vesicle at the tip of the 

 broadly conical evacuation tube, quickly becoming separated and 

 undergoing their final maturation at the orifice, the vesicle almost at 

 once disappearing; gametangia similar to the zoosporangia; oospore 

 spherical, colorless, 12-15 u. in diameter, with a thick smooth wall and 

 a large eccentric globule, lying loosely in the gametangium, germination 

 not observed; male gametangium conveying its contents into the female 

 through a pore formed in the cross wall. 



Parasitic on adults and eggs of rotifers, Sparrow (he. cit.), Great 

 Britain, Denmark; on rotifers, soil, Sparrow (1952c: 105), Cuba. 



It is pcssible that the tubular branched thallus shown by Sparrow 

 (1936a: pi. 19, fig. 9) belongs to a species of Lagenidium rather than to 

 Myzocytium zoophthorum. The lobed thallus observed in adult rotifers 

 recalls the imperfectly known M. lineare and, when these lobes are 

 very pronounced, a species of Lagenidium, to which genus the fungus 

 may possibly be referable. No specialized antheridial branch, outgrowth, 

 or fertilization tube is ever formed, however, as is generally true of 

 Lagenidium. 



The zoospores are predaceous and attack moving adult rotifers, 

 possibly attaching themselves by a mucilaginous secretion to the 

 carapace of the host. The animal continues its activities until the 

 thallus is well developed, when death ensues. 



Myzocytium microsporum (Karling), comb. nov. 



Lagenidium microsporum Karling, Lloydia, 7: 328, figs. 1-34. 1944. 



"Thalli usually unicellular, up to 40 in a host, oval, 5-15 X 6-25 [i, 

 spherical, 6-20 u,, pyriform or oblong and uniseptate. Sporangia usually 

 of same size and shape as thalli with one broad, 4 x 5 \x, or long, 6 x 20 

 (x, exit tube. Zoospores fully delimited in sporangium, forming a globu- 

 lar mass at exit orifice but soon swimming away without encysting; oval, 

 2.5 x 3.5 [i, slightly flattened and bean-shaped, coming to rest inter- 

 mittently and rounding up but apparently not withdrawing flagella and 

 encysting; diplanetism doubtful. Oogonia oval and spherical, 12-18 u, 

 in diam., slightly utriform and pyriform; antheridia predominantly oval, 



