914 AQUATIC PHYCOMYCETES 



cit.) no separation of the contents of the sporangium could be observed 

 prior to discharge. At maturity the protoplasm flowed out in a contin- 

 uous stream into a constantly expanding vesicle. There the mass quickly 

 began to rotate and, after a few seconds, was cleaved into parts, each 

 of which in turn assumed individual somewhat amoeboid motion. The 

 zoospores, after forming their flagella and taking on their mature 

 beanlike shape, are liberated upon the disappearance of the vesicle. 



Variations from the types of zoospore discharge described by Zopf 

 in Myzocytium and Lagenidium have been reported by a number of 

 investigators. In Myzocytium (Dangeard, 1903b; Thompson, 1934) the 

 zoospores have been observed to form within the sporangium and to 

 initiate motility there. The vesicle was completely absent in the material 

 studied by Thompson, whereas it was quickly evanescent in Dangeard's 

 fungus. In M. zoophthorum (Sparrow, 1936a) the zoospores were more 

 or less fully formed in the sporangium and completed their maturation 

 without a surrounding vesicle at the tip of the discharge tube. In 

 Lagenidium even more marked departures have been noted. In L. 

 cyclotellae, for example, Scherffel (1925a) has observed the zoospores 

 to be completely formed and moving within the sporangium before 

 discharge. He regards these bodies as primary zoospores. Scherffel 

 (op. cit.) also states that in L. oedogonii the zoospores are sometimes 

 formed as in Pythium, but that at other times they divide and move 

 within the sporangium, and at discharge form, as in Achlya, a clump of 

 cysts at the orifice of the discharge tube. From each of these cysts a 

 secondary zoospore emerges. Couch (1935b) noted only the Pythium 

 type of discharge in L. oedogonii. In L. marchalianum the zoospores 

 may be delimited within the sporangium and complete their maturation 

 in the extramatrical vesicle, after discharge. A somewhat similar con- 

 dition has been noted in L. oophilum (Sparrow, 1939c). Here, however, 

 the vesicle is apparently completely lacking. 



Striking examples of variation in zoospore discharge are provided by 

 three lagenidiaceous parasites of rotifers described by Karling (1944g). 

 In Myzocytium (Lagenidium) microsporum the zoospores become fully 

 delimited within the sporangium, are liberated, and form a mass at the 

 orifice of the discharge tube, where they undergo final maturation and 

 develop their flagella. In Lagenidium parthenosporum, although again 



