Phylum Opisthokonta [113 



They convert sugars to lactic and succinic acids, producing no CO2; the acids, if not 

 neutralized, check the growth of cultures (Emerson and Cantino, 1948; Cantino, 

 1949). Blastocladia appears to have lost the capacity to carry on the aerobic stages of 

 energesis, thus reverting to the type of metabolism characteristic of the supposedly 

 most primitive bacteria. 



In Blastocladiella, the basal cell bears a single reproductive structure. DiflFerent 

 species have the same three types of life cycle which occur in Allomyces (Couch and 

 WhiflFen, 1942). In Sphacrodadia the vegetative body is reduced to the unicellular 

 condition which is characteristic of the following order rather than of this. The life 

 cycle is of the complete homologous type. 



Order 2. Chytridinea [Chytridineae] (Schroter) Campbell Univ. Textb. Bot. 



152 (1902). 

 Orders Myxochytridinae and My cocky tridinae A. Fischer in Rabenhorst Kryp- 

 tog. Fl. Deutschland 1, Abt. 4: 20, 72 (1892), not based on generic names. 

 Order Chytridiales Auctt. 



Further synonymy as of the name of the phylum. 



Opisthokonta which consist entirely or largely of more or less isodiametric bodies 

 called centers: the centers may send out filaments more slender than themselves, 

 generating at their ends further centers; or may be capable only of producing rhizoids, 

 i. e., tapering absorptive filaments; or may be by themselves complete individuals. 



The chytrids are commonly thought of as prevalently parasitic on algae and 

 higher plants. They attack also rotifers, insects, nematodes, and other minute animals; 

 some parasitize other chytrids (Karling, 1942, 1948). It is probable, however, that 

 the majority of the group are saprophytic on organic remains. Some have been 

 cultured with no other organic food than cellulose (Haskins, 1939); new forms 

 have been discovered by baiting with, and culturing on, chitin (Karling, 1945; 

 Hanson, 1946) or keratin (Karling, 1946, 1947). 



The following varieties of vegetative structure may be noted, (a) A zoospore, 

 settling upon the surface of an appropriate host or substratum, may penetrate this 

 by means of a walled filament which develops a terminal center; the center then 

 sends out rhizoids, and also filaments which generate further centers, (b) Develop- 

 ment may be as above except that only one center is formed. The body thus described 

 is of the Entophlyctis type of Sparrow (1943). (c) The zoospore may itself become 

 the single center, penetrating its host or substratum only by rhizoids. The resulting 

 body is of the Chytridium type if the center is in contact with the host or substratum, 

 of the Rhizidium type if it is not. (d) The protoplast of the zoospore may migrate 

 into the protoplast of the host and there become a center without rhizoids; the 

 resulting body is of the Olpidium type. To the varied bodies thus described, the 

 following terminology is applicable: 



Pluricentric, with more centers than one; mono centric, with a single center. 



Intramatrical, the center developing within the substratum or host; alternatively, 

 in a host, endobiotic. 



Extramatrical or epibiotic, contrary to the foregoing. 



Eucarpic, the center not constituting the entire body; holocarpic, the center con- 

 stituting the entire body. 



The center regularly remains uninucleate during the vegetative phases and then 

 becomes the seat of successive simultaneous nuclear division, of cleavage, and of the 

 maturation of zoospores. Thus it is converted into a sporangium. In many forms, the 



