Phylum Opisthokonta [111 



chytrium, it appeared to Karling (1937) that the nucleolus generates the flagellum. 

 Within the developing swimming cell a body of granules assembles and produces a 

 "cap," prominent in stained material, on the anterior side of the nucleus, that is, on 

 the side away from the flagellum. 



Nowakowski (1876) observed sexual processes in Polyphagus, and Scherffel 

 (1925) observed them in many other chytrids. Sexual processes were known in 

 Monoblepharis from the discovery of this genus, and have been studied in detail in 

 Allomyces by Emerson (1939, 1941) and Emerson and Wilson (1949). 



The group thus characterized is of fewer than three hundred known species. One 

 takes no satisfaction in making it a phylum, but feels constrained to do so by its 

 isolation. Note has been taken that other groups including organisms of chytrid 

 body type, as Hyphochytrialea, Lagenidialea, and Phytomyxida, have nothing to do 

 with the proper chytrids. Furthermore, it will not do to thrust the proper chytrids 

 in with the groups of colorless flagellate and amoeboid organisms treated below as 

 phylum Protoplasta. One does not trust that group as natural, but it has a morpo- 

 logical continuity which would be defaced by the addition of this one. 



Vischer, 1945, coined the name Opistokonten for organisms whose motile cells 

 have posterior flagella. Gams (1947) listed as such the green organisms Pedilomonas 

 and Chlorochytridion; the choanoflagellates; the proper chytrids; the Sporozoa (the 

 whole group by virtue of such examples as have flagellate stages); and the proper 

 animals. He inferred that these groups make up a major natural group derived 

 from the lowest green algae. This interesting hypothesis must as yet be treated as 

 far-fetched. Pedilomonas is scarcely known; it was described by Korschikoff, 1923, 

 as a green flagellate of somewhat the appearance of a Chlamydomonas lacking one of 

 its flagella. The flagella of the choanoflagellates are pantacroneme instead of acro- 

 neme. There remains a striking resemblance between the motile cells of the proper 

 chytrids and the sperms of animals. The nuclear cap of the former is quite similar, 

 in development and structure, to the beak of the latter. 



The Opisthokonta are reasonably treated as a single class. 



Class ARCHIMYCETES (A. Fischer) SchaflFner 



Synonymy of the phylum. 



Characters of the phylum. 



Previous authors have arranged these organisms in a sequence from strictly uni- 

 cellular forms to typically filamentous forms. In the following treatment, this sequence 

 is reversed. The course of the evolution of the group is unknown, and it seems reason- 

 able to place the body types in the same sequence as among the Oomycetes. The class 

 is treated as two orders, Monoblepharidalea, essentially filamentous, and Chytridinea, 

 unicellular or producing filaments which taper or are swollen at intervals. 



Order 1. Monoblepharidalea [Monoblepharidales] Sparrow in Mycologia 34: 115 



(1942). 

 Suborder Monoblepharidineae Engler and Prantl Nat. Pflanzenfam. I Teil, Abt. 



1: iv (1897). 

 Blastocladiincae Petersen in Bot. Tidsskr. 29: 357 (1909). 

 Order Blastocladiales Sparrow 1. c. 

 Opisthokonta whose bodies consist of filaments of uniform diameter, or are of 

 types apparently immediately derived from this. Saprophytes in fresh water or soil, 

 chiefly on vegetable remains. There are two families. 



