304 NOTES ON INOCULATION OF FISHES WITH SAPROLEGNIA FERAX. 



dace, and it has at different times been observed to grow freely on 

 pieces of bladder, young cockroaches, and a variety of other hosts. 

 In the autumn of last year oospores were formed on it within a 

 week of their corresponding appearance in the previous year,* — 

 and this year they were first detected on January 29th, two days 

 before their first occurrence last year. 



" The first inoculation experiment of the present series was 

 begun on February 1st, when oospores were few in number. The 

 fish was a healthy Salmo fario, and the inoculation was made (as 

 in all following cases) by rubbing several Hies bearing the fungus 

 on the top of the fish's head without any abrasion of the epidermis. 

 The disease was first observed on the fourth day in the form of a 

 patch of numerous short filaments on the region rubbed. From 

 this it extended gradually, and the fish (as in all other cases 

 described here) showed symptoms of irritation, followed after a 

 time by languid movements, and finally died on the fourteenth day 

 after inoculation, February 15th. On February 12th another 

 inoculation was made, the conditions being precisely the same as 

 the last, except in this respect — that the fungus used bore many 

 oospores, but very few ripe zoosporangia. No appearance of 

 successful inoculation followed, and on the 20fch, after I had given 

 up all hope of any result, I went to Scotland for a fortnight, leaving 

 the fish in an apparently healthy state. Eeturning on March 6th, 

 I was surprised to find it extensively diseased, and in fact dying. 

 It died on the following day — three weeks and two days after 

 inoculation. A few oospores were found on the fungus growing on 

 the fish, as sometimes occurs in other cases. I may venture to put 

 forward here a supposition, which seems to me to throw light on 

 this case. The material used was, as already mentioned, rich in 

 oospores, but bearing few ripe zoosporangia. I have frequently 

 observed oospores germinate in ' hanging drop ' cultivations after a 

 period of about a fortnight. Supposing this inoculation was effected 

 by the product of oospores germinating after such a period, the 

 remaining time was sufficient for the development of the fungus to 

 the condition observed on my return. Most unfortunately, and to 

 my great regret, I left no arrangements for having the fish watched 

 and its appearance noted, as I had quite given up hope of result 

 from the experiment, and in the absence of evidence this supposition 

 is ventured. 



"At an early period of the late Fisheries Exhibition a consider- 

 able number of fish died in the aquarium from the disease, and this 

 was coincident with the presence of much lime in the water from 

 the newly-constructed artificial rockwork. To determine the part 

 played, if any, by lime in the water in cases of disease, Prof. Huxley 

 suggested to me certain experiments, of which the following is the 

 result : — 



" On March 7th two healthy S. fario were inoculated in the 

 manner just described. In both cases the disease appeared on the 

 third day, progressed in the fashion described, and the fishes died, 



* In a cultivation of different origin. 



