438 BULLETIN OF TPIE UXITKD STATES FISH COMMISSIOM. 



Saprolegnue, is capable of living and flourishing- on a variety of dead 

 animal matters. 



When the Saprolegnia is established on one such substance it is easy to 

 transmit it to another. The Saprolegnia obtained from diseased salmon 

 was thus cultivated for many weeks (from the end of December, 1881, 

 to the first week in Ai)ril, 1882) in the hope of obtaining the oosporan- 

 gia and thus identifying it with one or other of the described forms of 

 the S.ferax group. Up to the last-mentioned date, however, no oosporau- 

 gia appeared on any of these cultures. The course of events was this : 

 for two or three days zoosporangia were very abundant, and thousands 

 of zoospores were set free. But in no case which came under observa- 

 tion for several months were these zoospores provided with cilia, or 

 actively locomotive. They were discharged from the zoosporangia as 

 simple spherical corpuscles, which flowed passively away, and were very 

 often seen germinating by sending out a single delicate hypha. Im- 

 mense numbers of these spores accumulated among the hypha?.* 



After this condition had lasted for a day or two, the ordinary zoospo- 

 rangia diminished in number, and "dictyosporangia" made their ap- 

 pearance in place of them. In other words, the spores, instead of being 

 discharged, were retained within the zoosporangium, and began to 

 germinate in that position. 



At the same time, the protoplasm accumulated in certain regions of 

 the hyphffi, which often became swollen, and these accumulations were 

 shut off from the rest by transverse partitions. The hyphre thus as- 

 sumed a jointed or beaded appearance, as in the 8. torulosa of De Bary, 

 and the joints might eventually seijarate from the intervening empty 

 parts of the hyphse, as a sort of buds or gcmma\ which, after detach- 

 ment, might begin to germinate by throwing ont delicate hyi)ha? at one 

 or many points. Sometimes tliese buds were terminal and spheroidal 

 and closely simulated oosporangia, but they did not give rise to oospores. 

 No trace of antheridial branchlets was ever visible. 



In the third week of April, however, oosporangia and antheridia, in 

 all respects similar to those of the "mouofcrt " form of Saprolegnia fcrax, 

 made their appearance in a copious growth of the fungus on a fly, which 

 was infected on the 24th of March from a culture on bladder, which was 



* Among previous observers, Mr. Stirling and Mr. W. G. Smith describe and figure 

 locomotive zoospores as if they were of ordinaiy occurrence. Mr. Brook, on the other 

 band ("Notes on the Salmon Disease in the Esk and Eden." Transactions of the 

 Botanical Society of Edinburgh, 1879), appears never to have seen locomotive zoo- 

 spores; and Mr. George Murray, of tbe Botanical Department of the British Museum, 

 wbo luis been kind enougb to make a seri(^s of observations and experiments, con- 

 tinued over six or seven weeks, on crops of Saprolegnia, raised upon dead flies infected 

 from Conway salmon, has met with the same negative results. Quite recently, how- 

 ever (March 1(5), locomotive zoospores have been emitted from one of our specimens of 

 salmon fungus cultivated on bladder. But, as in our specimens, so in those cultivated 

 by Mr. Murray, no trace of oosporangia had appeared up to that time. 



