The Fungus of Salmon Disease. 63 



. These oospores, then, are what are termed the " resting 

 stage," or ''resting spores," of the plant. All fungoid life, in- 

 cluding bacteria, requires such a resting spore to carry it 

 over any prolonged unfavourable conditions likely to overtake 

 it, much in the same manner as grain matured in an ear 

 of corn, which can be made to grow years after it is har- 

 vested ; though in the case of our aquatic fungus the period 

 of torpidity need not be longer than from winter to summer ; 

 and, indeed (as it appears well able to grow all the year round), 

 this provision seems to be meant to provide against long 

 periods of starvation, or other unfavourable influence, rather 

 than against winter weather. 



The vitality and distribution of these spores of both kinds 

 seems open to observation and study. In the wet condition as 

 liberated in the water, it is probable that during epidemics, or 



On the 8th of May I obtained full confirmation of this result in an independent cul- 

 ture, made also on the ist May — that is, developed in 7 full days. 



On the 9th May, I set up a series of 12 drop cultures for continuous observation, 

 but an invasion of achlya unfortunately got the upper hand of the better part of them ; 

 however, I was able to obtain positive results in two of the cultures, and in four days 

 had well-defined oospores, though not in very numerous examples. 



Again, on the morning of the 8th of June I cut some small pieces of healthy skin 

 from a salmon, and immersing them with some small diseased portions of the same 

 fish, in a large glass cylinder, with an arrangement to maintain a constant stream of 

 running water at frequent intervals, .for several consecutive hours at a time, during the 

 first two days. I was able to get a good growth on the small portions of healthy skin, 

 and these were then removed lor cultivation to fresh glasses, and I obtained on them 

 visible oospore formation in 3.$ days — that is, on the evening of the nth June. The 

 oosporanges here were few, and growing on the filaments that had ordinary sporanges 

 at their extremities, and the characteristic antheridial branches were in every case 

 absent ; but this is not unusual, and the oospores were, in my opinion, capable of ready 

 growth in the normal manner. 



These observations, I think, show that the generally supposed necessary condition of 

 a low temperature is not at all requisite to oospore development (and I may add that I 

 obtained a single result of the same kind during the very warm weather of 1887, the 

 development then, however, being accompanied by antheridial branches). They also 

 show that oospores can be produced with comparative ease in four or five days, and 

 that they can grow directly from a diseased fish. Against this, the ordinary growth of 

 the fungus when in favourable laboratory culture is not likely to produce them, and, 

 having such a culture, it is difficult to cause ready oospore formation, even with studied 

 variety in the supplied conditions of growth. 



