376 



Part III — Seventh Annual Report 



believed all that is necessary is to place a dead fly for a day or two 

 in rain water, when it will soon become enveloped in it. This experi- 

 ment has been performed by Mr Stirling, Mr Murray, and latterly by 

 myself, but in each case our experiments have been unsuccessful. 



In my case, flies have only, been obtained with difficulty owing to the 

 season of the year, and the specimens used were those which I managed 

 to discover lying in odd corners, so that when they gave rise to cultiva- 

 tions of common moulds I have not been much surprised ; still, however, 

 the same result seems to have attended the experiments of the previous 

 observers noted. Prof. Huxley and Mr George Murray have, however, 

 easily infected dead flies by rubbing them over diseased fish and even by 

 placing them in water in which Saprolegnia was placed. The exact 

 procedure adopted in their case was to insert a glass tube into a wide 

 glass vessel, in such a way that the bottom of the glass tube did not quite 

 reach the bottom of the glass vessel. Flies were then allowed to float 

 on the surface of the water in the glass vessel, but outside the tube, 

 while in the tube itself an already infected fly was placed. The flies 

 then in the outer vessel becoming infected, showed that the spores 

 liberated from the fungus affecting the fly in the central tube must have 

 passed first toward the bottom of the tube and then out of it, before 

 they could be able to rise in the outer part and infect the dead healthy 

 Hies. This experiment demonstrates that a very considerable power of 

 locomotion must be possessed by the liberated spores. 



Mr Stirling attempted to infect healthy minnows by placing a piece of 

 skin, with fungus adhering to it taken from a salmon smolt, in a glass 

 vessel filled with water in which the minnows were placed along with it, 

 but found that 'In three days they had eaten up both skin and fungus and 

 remained unaffected.' Considering that possibly the fungus was dead, he 

 procured fresh pieces of skin with fungus which had been removed from 

 fish at the water side and immediately placed in bottles of water. These 

 fresh pieces were then emptied into the glass vessel containing the 

 minnows and the water left unchanged for three days. At the end of 

 this time the water was changed, and subsequently renewed every second 

 day. Here, again, a like result attended his experiment, as the minnows 

 devoured every morsel of skin and fungus and remained alive and healthy 

 for two months afterwards, when they were last observed. I am inclined 

 to attach a certain measure of importance to this experiment for reasons 

 which will appear later. In 1882-3 Mr G. Murray, at Professor Huxley's 

 request, made a series of experiments with fungus cultivated on the 

 bodies of dead flies, with somewhat varying results. 



Receiving from Professor Huxley on the 2nd February cultivations of 

 fungus derived from a diseased Conway salmon, he proceeded to keep up 

 fresh cultivations on flies, and in the July immediately following he attempted 

 inoculation of two healthy specimens of trout and two healthy dace, by 

 rubbing them with fungus, making in addition a slight abrasion of the epi- 

 dermis in one trout by rubbing it with tine sand. No result attended this 

 experiment which had been made with fungus on which no oospores were 

 present. This experiment was then repeated at a later date with 

 fungus bearing oospores and zoosporangia, but in this case the site of 

 inoculation was changed, the left side of the fish being now chosen. 

 This time the experiment was quite successful, and it was inferred that 

 the success was due either to the presence of oospores in the fungus or 

 to its being applied to the new site. In order to test this, two dace were 

 rubbed on the sides with fungus in which no oospores were present, but 

 on which there were to be found a plentful growth of ripe zoosporangia. 

 This experiment resulted in complete success, and he states that 1 on 



