I9I9] 



WES TON—DICTYUCH US 



293 



that is customarily ascribed to the genus, nor has this phenomenon 

 been reported in the case of other members of the family. In Pyth- 

 iwwi, however, which is more or less closely connected with the Sapro- 

 legniaceae, according as one or another of the several theories of 

 relationship is accepted, a similar double swarming of laterally 

 bicihate zoospores has been reported. Cornu (3) in 1872 first 

 noted the fact as follows: "les zoospores dans tous ces genres 



<^ 



Q 



Saprolegnia 



Achlya 



Thraustotheca 



Dictyuchus 



Aplanes 



Fig. I. — Comparative view of cycles of non-sexual spore formation in main 

 genera of Saprolegniaceae; diagrams, of approximately same scale, from drawings 

 of living material, except in case of Aplanes, which is after DeBary's figure. 



germent en dormant lieu a un filament . . . ou bien elles 

 emittent des zoospores semblables a elles-memes (ex. Pythium 

 proliferum et ses var.)." Recently Butler (2) has corroborated 

 CoRNu's observations by describing and figuring the process in 

 the case of Pythium diacarpum. In spite of the apparent rarity 

 of this phenomenon, however, the writer ventures the opinion 

 that further investigations will bring to Hght other cases, not 

 only in Dictyuchus, but also in related genera of the Saprolegnia- 

 ceae. 



The significance of this repeated zoospore emergence in Dic- 

 tyuchus is a matter of some interest. One may, of course, regard 

 it as a regular but hitherto unobserved stage of the life cycles of 



