NOTES ON INOOUIiATION OF FISHES WITH SAFROLKGNIA FERAX. 307 



an ordinary temperature soon kills it. The fact that I ceased to 

 find worms bearing Saprolegnla as the summer advanced I attribute 

 to the great dryness which resulted from the exceptionally hot 

 weather. 



" The immediate cause of the outbreak having been thus 

 ascertained, the grave question remained, — where did the earth- 

 worms obtain the SaproUytda ? I procured worms from various 

 parts of the country, including the neighbourhood of a river [the 

 Tweed] which contained diseased fish, and on none of these could 

 Saprolegnia be reared without inoculation. I continued to find it 

 on earthworms — though not on all — procured from a piece of waste 

 ground adjoining the Fish Culture Museum, and it soon became 

 notable that worms only from a certain region (a few yards in 

 diameter) of this ground yielded the fungus. It could never be 

 found on those dug up in the adjacent grounds of the Natural 

 History Museum. Now, over the particular region indicated there 

 were lying a number of fish-bones, which at once aroused curiosity. 

 The remarkable results obtained by M. Pasteur in his observations 

 on earthworms as carriers of infectious material suggested a clue 

 to the way out of the difficulty, though I was unwilling to believe, 

 as 1 am now, that this aquatic fungus could maintain life for any 

 length of time in the ground. However, the discovery that the 

 bones just mentioned belonged to certain fish which had died in the 

 tanks erected by the Fisheries Exhibition Commissioners, and had 

 been so cast out there a few months before, seemed to point in the 

 direction which my suspicions took. Mr. Edon (to whom I am 

 much indebted for assistance throughout this enquiry) informed 

 me, however, that to the best of his knowledge worms for food 

 were never dug up in that particular place, and its appearance bore 

 out his belief. Matters remamed for some time in this unsatisfactory 

 position, until, in going over the ground one day, I observed a 

 labourer digging in the very region which had been infected. On 

 questioning him he succeeded in remembering having once or twice 

 in rainy weather earlier in the year obtained his worms from there. 

 (It was near shelter.) The agreement thus established forces upon 

 me the conclusion that the infectious material was obtained from 

 the dead fish cast out, — that during the damp weather it remained 

 alive in its resting-state, and was spread abroad in the ground by 

 earthworms, and that it was finally conveyed by them into the 

 tanks where the outbreak took place. Later in the year, as 

 described, this source of infection was dried up, while the outbreak 

 was stopped by the precautions Mr. Edon took in his treatment of 

 the fish. 



" Towards the end of November a species of Bictyuclnis hitherto 

 unknown to me began to appear along with the Saprulci/nia in the 

 cultivations. It rapidly increased in power, and in the course of a 

 few days obtained complete possession ; and the Sajirolc<i)tia, which 

 had first been placed in cultivation three years before (all but a few 

 days) by Prof. Huxley entirely disappeared. The suddenness and 

 completeness with which it was driven from the field were highly 

 impressive, as well as not a little annoying after a period of 



