ON THE SAPKOLEGNIEiE. 197 



am confident the disease would be checked, if the otters, just 

 for a change, were protected for a year or two. The course of 

 the salmon-disease and the grouse-disease tells us, in unmistakeable 

 language, to beware of altering the balance of nature. Left 

 to herself, the great law of the ' survival of the fittest,' would 

 always keep nature's numerous family in a prosperous and 

 healthy condition." We might enquire which has destroyed the 

 largest per-centage of fish — the otter or the disease ? Which left 

 the survivors in the best condition to fight the battle of life in the 

 succeeding seasons? Probably, few would hesitate to welcome 

 back the otters, if they could be assured that thereby the dis- 

 ease would be controlled. Yet we may rest assured that it is 

 quite hopeless to think of killing off the fungus. We have not 

 killed the potato-disease, and have no prospect of doing so. If 

 success is to be achieved, it must be, by restoring to the salmon 

 such a constitution as will enable it to defy the attacks of its 

 parasites. 



I have dwelt at length on the genus Saprolegnia, as being the 

 representative genus of the family ; but there is strong reason to 

 suppose that Achlya has, also, a large share in the work of destruc- 

 tion which we have been considering, and Leptoi7iitus has also been 

 found parasitic on fresh-water fishes ; the other genera seem to 

 flourish principally on dead organic remains, whether animal or 

 vegetable. 



The following is the list of works referred to in the above 

 paper : — Grevillea, Vols, i, 6, and 9 ; Annales des Sciences Natu- 

 relles, Vol. 15; Quart. Journ. Micro. Sci. for 1867, 1882, and 

 1883; Ray Society's Proceedings for 1845 and 1853; Commis- 

 sioners' Report on the Salmon-Disease {Eyre and Spottiswoode) ; 

 Berkeley's Cryptogamic Botany and British Fungology ; Micro- 

 graphic Dictionary; Science Gossip for 1865 ; Cooke's Handbook 

 of Fungi ; and Fungi {International Scientific Series) ; The 

 Microscope, Carpenter. 



