ORDER MYXOBACTERIALES 1011 



conclusion that the family Archangiaceae should be abandoned (Krzemieniewski 

 and Krzemieniewska, Bull. Acad. Pol. Sci. Lettres, Classe Sci. Math. Nat., S^r. B., 

 Sci. Nat., I, 1937, 11-31) and the genera and species redistributed. The validity 

 of the argument is accepted, but the family is retained until a satisfactory revision 

 can be effected. This should be based on a careful comparative study of the species. 



Key to the Families of Order Myxobacteriales. 



I. Neither definite fruiting bodies (cysts) nor spores (microcysts) produced. 



Family I. Cytophagaceae, p. 1012. 

 II. Spores (resting cells, microcysts) produced. 



A. Restingcells (spores, microcysts) elongate, not spherical or ellipsoidal. Fruit- 



ing bodies (cysts) produced. 



1. Fruiting bodies (cysts) not of definite shape; cells heap up to produce 



mesenteric masses or finger-like (columnar) bodies. 



Family II. Archangiaceae, p. 1017. 



2. Fruiting bodies (cysts) of definite shape. 



a. Cysts usually angular. Vegetative cells usually thick and short, 

 with blunt, rounded ends. 



Family III. Sorangiaceae, p. 1021. 

 aa. Cysts usually rounded. Vegetative cells long and thin, sometimes 

 spindle-shaped with pointed ends. 



Family IV. Polyangiaceae, p. 1025. 



B. Resting cells (spores, microcysts) spherical or ellipsoidal. Fruiting bodies 



produced except in genus Sporocytophaga. 



Family V. Myxococcaceae, p. 1040. 



