5128 Fishes. 



current of water through their nests is probably intended to prevent 

 similar occurrences. Valentin has also noticed it on the eggs of the 

 Bufo obstetricus; Pennant described it as it occurred upon roach kept 

 in glass vessels, and it is well known to attack various species of carp, 

 especially our well-known favourite, the Cyprinus auratus, or gold-fish. 

 Of its occurrence on this animal we have a description by Dr. Bennett, 

 in the Edin. Philos. Transactions. Finally Kutzing has described 

 three species (which I believe to be all identical), one of which is 

 termed the Saprolegnia xylophila, and found growing upon twigs in 

 water. I too have likewise, in my researches, obtained it growing 

 upon twigs, identical in its nature with his drawings and with the plant 

 as it grows upon the bodies of living and dead gold-fish, and derived 

 originally from them. 



Further research on this subject has obtained for me the information 

 that the Saprolegnia capitulifera has been observed by Alex. Braun to 

 develope freely on decaying pieces of Nuphar pumilus, and also rapidly 

 to attach itself to flies falling into the water in the localities where it 

 thus grows on the plant. This plant, which fully deserves its name of 

 Saprolegnia ferox, as it fell under my notice, occurred amongst a num- 

 ber of young gold-fish, about twenty-five in number, kept in a parlour, 

 contained in a round glass jar along with four young minnows. The 

 gold-fish had been obtained from the Botanic Gardens of the Royal 

 Dublin Society at Glasnevin, in September, 1855, having been bred 

 there in the Victoria-lily house during the previous summer months: 

 they were of small size, varying in length from one to two inches ; 

 and, as 1 had obtained them for the purpose of making a series of 

 observations upon the changes which they undergo in colour during 

 their growth, 1 had them in every stage — gold, silver-coloured and 

 white, and also dull brown. On the 28th January, 1856, 1 first noticed 

 that two of these fish had each an extremely beautiful white tuft, 

 resembling somewhat the appearance of common mould, upon its 

 side : the extent of this patch of vegetation was not more than the 

 size of a spangle. The fish were swimming about briskly, and 

 appeared in perfect health, and I am certain there could not have 

 been any extent of this plant — at least sufficient to be visible to the 

 eye — present upon them twenty-four hours previously. I instantly 

 isolated the two attacked for observation, washed out the jar, and re- 

 placed the other fish in it: they were still, to all appearance, healthy 

 to the most minute scrutiny. In the course of twelve hours more the 

 plant had rapidly extended in the two fish, occupying fully twice as 

 much of the surface as it did in the morning, and next morning 





