87 



out being studied, or even noticed as a fungus disease. Mr. Andrew Brotherston 

 (Kelso), in his prize essay International Fisheries Exhibition, Edinburgh, 1882, 

 reports the appearance of a disease on bull trout in the Eden 36 years ago, and 

 the fact of having counted as many as 35 dead salmon in a distance of 100 yards 

 in the Tweed itself in the spring of 1872. The late Mr. Stirling (Royal Society, 

 Edinburgh, Proc, 1879-80,) recorded several epidemics at Igtham, in Kent, one 

 of them dating as far back as 1850. These diseases were probably identical with 

 the Snprolegnia ferax now under consideration. 



This disease is so clearly of an infectious or contagious character, that where 

 fish are plentiful and subject to the same influences, many must die ; but it is 

 interesting to have the positive information that notwithstanding the serious 

 mortality it has caused amongst the salmon for several years past, the supply 

 even from the infected rivers has been increased rather than lessened. This 

 fact seems to show that it is in some way connected with a great increase in the 

 number of the iish, and that overcrowding may be as fatal to salmon as it is 

 known to be with grouse. 



The fungus which constitutes the disease ( Saprooh'jnia ferax) has been under 

 scientific observation for many years. It is propagated with great rajjidity on any 

 dead organic matter, and we know well now that it becomes a parasite on livmg 

 freshwater fishes, and has the power of quickly killing them. The fungus, like 

 many other microscopic funguses, presents a different form when grown in the air 

 from that in which it appears when grown under water, and it ia much more 

 common than is generally supposed. 



A similar fungus has long been known to affect the common house flies in 

 autumn. The fly is first noticed to become gray in colour, stupid, or " muzzy ; " 

 it then dies, and maybe found adherent to windows, ceilings, walls, 4c., very 

 firmly fixed to the object by its proboscis, and with its legs weU spread out. 

 If seen at this time upon the windows it pre^^ents the appearance of having 

 swollen and burst, with a well marked spray surrounding it. 



A miscroscopical examination reveals the fly to be surrounded by numerous 

 round spores like white globules, and having transparent tubular threads pro- 

 ceeding like rays from between the rings of the abdomen, terminating in rounded 

 extremities, and enclosing the globular spores which in the act of maturation are 

 discharged from the extremities of the tubes, giving the appearance of ground 

 glass efflorescence surrounding the fly. 



If the diseased fly be placed in water, it will be observed in a few days to be 

 covered with a fluffy cottony web, with all the characteristics of the salmon disease. 

 This fungus upon the fly has the name of Empuia musca, or Sporendonema 

 musccE, and when this plant is produced in water it becomes the Sapi-oUgnm ferax, 

 or the fungus of the salmon disease-the fungus of the fly being the form when 

 grown in the air, and the fungus of the fish being the aquatic form of the same 



plant. 



If a fly, killed without breaking the skin, be rubbed against a fresh patch of 

 diseased skin from an infected salmon, and be then placed in water, it may in two 

 days develop traces of the salmon disease, and may infect any fish, especially upon 



