9 6 2 AQUATIC PHYCOMYCETES 



posteriorly, formed by successive divisions of the contents, escaping 

 by fracturing of the wall. 



Parasitic in the cytoplasm of Euglena, Cryptomonas. 



Pseudosphaerita Dangeard is apparently most closely related to 

 Olpidiopsis. Observations on the method of formation of the resting 

 spore will be necessary, however, to determine its precise affinities. 



The genus was founded by Dangeard to include Sphaerita-kke forms 

 with biflagellate zoospores. Although the thallus superficially resembles 

 that of Sphaerita, Dangeard (1933) has pointed out that the two fungi 

 may be distinguished by the different methods of zoospore formation. 

 In Sphaerita this is simultaneous. In Pseudosphaerita each division of 

 the nucleus of the thallus is followed by a division of the cytoplasm. No 

 mitotic figures were observed. At maturity the contents are cleaved into 

 from 64 to 128 polygonal uninucleated segments. These become flagel- 

 late zoospores and may swarm a long time within the sporangium before 

 being liberated. Occasionally, they are discharged within the host and 

 undergo germination in situ. The nucleus of these zoospores is larger 

 (2.5 (jl) than that formed in the swarmer of Sphaerita and possesses a 

 more or less central nucleolus. Although the method of zoospore 

 formation in Pseudosphaerita is unusual and led Dangeard (loc. cit.) to 

 suggest the erection of a separate family for the inclusion of similar 

 forms with a successive type of spore maturation, it is not unique and 

 has also been observed in the true chytrids. 



The parasite may develop and sporulate within the moving host or 

 may attack resting individuals. Puymaly (1927), however, observed that 

 Euglena viridis when attacked by a fungus called by him Sphaerita, but 

 having biflagellate zoospores and hence probably Pseudosphaerita, 

 quickly ceased its flagellar action after infection. It continued to show 

 signs of life until spoliation of the fungus occurred. He also noted 

 that the zoospores of the fungus were strongly attracted to the Euglena. 

 The method of infection, however, was not determined. Puymaly, 

 although recalling the conjecture of sexuality in Sphaerita proposed by 

 Chatton and Brodsky (1909) and based on observations of conjugation 

 in a Sphaerita-]ike organism by Doflein (1907), was certain that in his 

 fungus the biflagellate swarmers were zoospores and not zygotes. 



