60 Proceedings. 



This disease does not kill the fish, and is not Saprolefjna. 

 Saprolegna is, as far as we can speak positively of anything, 

 always fatal. I have seen hundreds of fish die from it, and 

 never one recover. Many theories have been advanced to 

 account for it, overcrowding being the principal. I have 

 seen no evidence of overcrowding producing it, though I do 

 not go so far as to say that it will not do so. I have seen 

 much overcrowding, but no evidence of Saprolegna arising 

 fifom it. The view that I take is that it arises from change 

 of temperature affecting the fish prejudicially, and reducing 

 it to a lowered condition, in which it is liable to the disease. 

 Some hold that it is infectious ; probably it is, but it will not 

 on that account necessarily aft'ect healthy fish. 



I think if we examine the cases of overcrowding fish being 

 affected we shall always find that at the same time there is 

 change of temperature, and this in my opinion is the time 

 cause. I wiU instance overcrowding where certainly the 

 disease is not induced. Take the warm engine-pools at miUs 

 where Goldfish swarm to an extent utterly unknown under 

 natural conditions, where numbers are kept down by the pre- 

 datory fish ; here there is no Saprolegna, But take some of 

 the fish, as I have done many times, and put them into a 

 globe, giving them water at ordinary temperature, and in a 

 few days the disease appears and carries oft' all, though some- 

 times one or two are unaffected and survive. The greatest 

 care is necessary in gradually accustoming the fish to cooler 

 water. To carry this instance further still : the Goldfish sold 

 by the aquarium-dealers of Seven Dials are generally accU- 

 matised and quite healthy, but immensely crowded. I have 

 taken fifty or so of these fish to Westmoreland, and placed 

 them in a large open pond of spring water ; nine-tenths have 

 always died of Saprolegna because the water was so much 

 colder than a London shop ; but here was no overcrowding. 

 Again, I have seen a globe in London filled with Sticklebacks, 

 and every one affected, a miserable sight ; yet the ponds from 

 which they are taken are always overstocked, yet perfectly 

 healthy. I have seen dead Sticklebacks in ponds, and dead 

 Koach in ponds teeming with them ; also Goldfish, but they 



