ON THE SAPROLEGNIE^. 191 



the zoospores ; the presence of undoubted sexual organs in the 

 individuals attacked; and the changes, disturbances, and hyper- 

 trophies which can be observed in the affected plant. He 

 proposes three divisions, or genera, — viz., one in which the 

 sporangia are entirely free in the filament of the plant affected ; 

 a second, in which the sporangia are partially adherent to the 

 filament ; and the third, in which the sporangia are surrounded 

 with a general membrane, which is itself adherent to the wall 

 of the affected filament. The names he has given them are 

 respectively Olpidiopsis^ Rozella^ and Woronina. 



We come now to the economic portion of our subject, espe- 

 cially the relation that exists between Saprolegnia and the Salmon 

 disease. The importance of the subject may be judged of from 

 the account of the ravages of this disease brought to light by the 

 enquiries of the Royal Commissioners. In the year 1850, a 

 severe fungus epidemic broke out amongst the fish in the ponds of 

 Ightham House, Kent, and the furred fish, as they were called, 

 died in large numbers. In the spring of 1874, a still severer epi- 

 demic broke out in the same ponds, and was made the subject of 

 investigation by Dr. Church, of St. Bartholomew's Hospital, who 

 satisfied himself that the fungus affecting the fish was the Sapro- 

 legniea. The roach, dace, and gudgeon suffered the most ; the 

 small pike and perch were affected, but the large pike, perch, and 

 the eels escaped. There is, however, very little doubt that the 

 disease had existed in this country in a sporadic form for many 

 years. So long ago as the spring of 1852, Dr. Crosbie, late sur- 

 geon to the Challenger expedition, investigated a case of the fungus 

 disease in a salmon taken from the Tweed, and found that fisher- 

 men, and others conversant with the river, were fairly well acquaint- 

 ed with the fungus. But in the spring of 1877, the disease assumed 

 an epidemic form in the rivers Esk and Nith ; it soon spread to 

 the Eden and adjoining rivers. In the spring of 1879, it was 

 observed in the Tweed, where it rapidly became serious ; and in 

 1880, when the Salmon Disease Commission was appointed, it 

 had extended to the Nith, the Annan, the Esk, the Eden, the Cree, 

 and the Dee, all flowing into the Solway Firth ; to the Doon and 

 the Ayr in Ayrshire ; to the Derwent in Cumberland, the Lune in 

 Lancashire, and to the Tweed. Since then the disease has broken 



