976 AQUATIC PHYCOMYCETES 



M. irregulare) characteristically exhibit this expansion. The fungus in 

 Closterium reported by Sparrow (1932b) is doubtfully M. prolif- 



erum. 



Although Myzocytium proliferum has been reported many times and 

 is well known (from the excellent illustrations of Zopf, 1884), more 

 data on the size range of parts are needed. The zoospores described by 

 Tokunaga, for example, are twice as large (10 by 6 [i) as those described 

 by Sparrow (5.4 by 3.6 \l). 



The sexual stage (Fig. 79 C) was first observed by Cornu (1869a). 



As Zopf pointed out (op. cit.), the species is most frequent in shallow, 

 stagnant, brightly lit water. It may occur in epidemic proportions from 

 spring to fall. 



In some instances of zoospore discharge the vesicle is so tenuous as 

 to be nearly invisible, and in certain specimens it may be entirely lacking 

 (Thompson, 1934). Chaudhuri (1931) stated that a fertilization tube 

 was not produced by the male gametangium. Since his observations 

 apparently refer to material fixed in formalin, the tube may have been 

 present but had soon been dissolved by the preservative. 



Myzocytium proliferum Schenk f. marinum Kobayasi and Ookubo 

 Bull. Nat. Sci. Mus. (Tokyo), 33: 64, fig. 9. 1953 



"Thallus endobiotic, elongated, unbranched, forming monilioid chain, 

 after maturity segmented in 3-6 or more zoosporangia and gametangia. 

 Zoosporangia in beadlike chains connected by thin outer membrane, 

 globose, ellipsoid or more longer, 10-20 [x in diameter, somewhat thick- 

 walled, colourless, each with a lateral discharge tube; tubes protruding 

 through the wall of host-cell, cylindric, contorted, 50-60 jx long, attain- 

 ing 280 [x, 5-6 fj. in diameter. Zoospores forming a vesicle at the orifice 

 of discharge tube, nephroid, 6 X 3 [x, with lateral two flagella. Male 

 and female gametangia commonly globose, intercalar. Oospore loosely 

 and singly formed within female gametangium, globose or ellipsoid, 

 commonly 15 [x in diameter, smooth, thick-walled, containing an 

 eccentric large oil drop" (Kobayasi and Ookubo, loc. cit.). 



Parasitic in Cladoplwra japonica, Japan. 



In Cladoplwra that had been cultivated in artificial sea water. Probably 



