yielded both monocentric and polycentric offspring, indicating that they may be totipotent for both types. However, in these preliminary experiments the monocentric isolate yielded a preponderance of monocentric thalli, while the polycentric isolate gave rise to a greater number of polycentric thalli throughout 6 successive generations. The polycentric thalli of these strains are strikingly similar in structure and general appearance to those of Catentaria. This similarity together with the presence of minute granules, side bodies, and conspicuous nuclear caps in the zoospores suggest that P. variabilis may be more closely related to Catentaria than to Phlyctorhiza.