62 The Fungus of Salmon Disease. 



Huxley in his Fishery Reports, that oospores are of very rare 

 occurrence, and that other observers, during periods of observa- 

 tion extending over several years, had only seen them on two 

 or three occasions. I am inclined to believe that these oospores 

 may, as " resting spores," be considered to resemble the ascospores 

 of yeast, which are also difficult to obtain, as from ordinary 

 yeast it requires a period of ten days, and starvation conditions, 

 to develop them. When working on ferments in the Biological 

 Laboratory of the Queen's College at Cork, four years ago, 

 I succeeded in obtaining a beautiful ascospore formation in 

 forty-eight hours, and was of course astonished at the rapid 

 production, but the yeast that gave this result was an accidental 

 infection from the plant houses, and I assumed that it was pos- 

 sibly grown from an ascospore, and that for this reason the 

 formation was more rapid than if developed from the ordinary 

 yeast cell, which may have been under previous favourable 

 cultivation (with no ascospore interval) for thousands of gene- 

 rations. I mention this, as I think it is also possible that our 

 salmon disease, under ordinary and favourable conditions of 

 zoospore culture, may become less and less adapted to readily 

 assume the oospore formation ; and it is the more likely, as ob- 

 servation has probably been confined to laboratory cultivation 

 under favourable conditions, or taken from salmon dying during 

 epidemics, whereas, had the salmon been these of isolated 

 cases in healthy rivers, the result may have been different.* 



* I have been able to obtain striking confirmation of this opinion during the 

 months of May and June of the present year. Starting with a Saprolegnia ferax 

 growth that had been in favourable laboratory cultivation since December, I after much 

 trouble (lasting over three months) got a gradual oospore formation, which received 

 every encouragement, until on the 1st May the oospores were plenty, and fully deve- 

 loped. Fresh flies were then inoculated from it, and on the 3rd of May a visible 

 young growth had occurred on them, which continued to grow favourably, and showed 

 full filaments and zoospore formation by the 4th of May. On the 5th of May I 

 observed the first tendency to form oosporanges, and on the 6th I was able to define 

 and make drawings of several true examples of fully-matured oospores — that is, in 5 days 

 and 8 hours after adding the fresh fly ; temperature varying between 49 and 58 Fahr. 



