CHYTRIDIALES 61 



dissolves in the water and liberates them. They then assume flagellar 

 action and swim away either at once or after undergoing a period of 

 collective swarming at or near the orifice of the discharge pore {Astero- 

 phlyctis, Siphonaria, Rhizidium mycophilam). Whether the slime is form- 

 ed from the substance of the papilla alone or from the inner wall of the 

 sporangium or from material between the spore origins (Nowakowski, 

 op. cit.) is not known. Observations on certain operculate forms, such 

 as Nowakowskiella etegans (Sparrow, 1933a) and Endochytrium oper- 

 culatum (Karling, 1937a), indicate that at least part of it is of papillary 

 origin. The formation of a vesicle into which the spores pass upon dis- 

 charge has been recorded by several workers (Zopf, 1884; Sparrow, 

 1931c, 1936a, 1937a; Karling, 1937c, 1945c; Antikajian, 1949; and 

 others). Owing to the minuteness of the structures involved, however, 

 and the tenuousness of such membranes, these observations require 

 abundant confirmation. 



A word might be said concerning the remarkable collective swarming 

 which has been noted in certain instances among both inoperculate 

 and operculate species. This phenomenon is perhaps most typical of 

 the small group of chytrids inhabiting insect exuviae (Sparrow, 1937a; 

 Karling, 1945c; Antikajian, 1949). In Asterophlyctis and Siphonaria 

 the emerged spores remain for a short time in a motionless cluster at 

 the basal orifice. Then a few on the periphery of the mass initiate in- 

 dividual motion, which ordinarily starts as a slight trembling of each 

 spore body. This increases in intensity and culminates in a violent 

 lashing of the spore from side to side. In a short time all are in motion, 

 and the group becomes a writhing mass of tugging individuals endeav- 

 oring to pull their flagella free from some apparently confining sub- 

 stance. After a few minutes of this wild activity, during which the con- 

 tour of the struggling group may become very elongated, occasional 

 spores dart from the mass. These are quickly followed by others, until 

 all have dispersed. In the new species Rhizidium chitinophilum Sparrow 

 (p. 412) the spore behavior is even more extraordinary. After discharge 

 the spores form a compact subspherical mass. Soon they fall apart, 

 and in about a minute each assumes individual movement. Instead of 

 darting away, however, the writhing mass moves about 10 \i or more 

 from the orifice and assumes a broadly reniform shape. After several 



