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IcntK})opntnirius multifilius 



REV. FREDERICK R. WEBBER, Cleveland Aquarium Society 





.-Aquarium vv'ifK Covei- Glass 



Electric Lamp 

 i^loat" 



fruit Jar* 



Glass Jar 



Vacuoles 



Ichthyophth'irius 



Parasite dividing 



5warm -spores 



Every aquarist knows Ichthyopthirius 

 multifilius, the parasitic infusorian which 

 destroys many tropical aquarium fishes, 

 as well as rainbow trout, brook trout, 

 and even carp, shad, pike and whitefish. 

 It exists both in the aquarium and in the 

 native haunts of fishes. The infested 

 fish hangs listlessly in the water, with 

 drooping fins. Now and then it "shakes" 

 violently from side to side. This wrig- 

 gling movement is almost constant dur- 

 ing the later stages. After a few days 

 the fish appears to be covered with small 

 white spots, like fine salt sprinkled over 

 its body. If examined closely, small pits 

 are discovered where the grains have 

 been. The fins are also affected. The 



cause is a small ciliated protozoan, from 

 one-half to less than one millimeter in 

 size. When examined under a micro- 

 scope, we find that the parasite is round, 

 of protoplasmic structure, and completely 

 covered with cilia. The contained pro- 

 toplasm is filled with round, somewhat 

 opaque granules, making the crescent- 

 shaped nucleus difficult to distinguish. 

 In some pustules two animals are found. 

 The young parasite is a free-swimming 

 creature, which moves rapidly through 

 the water, often in an irregular course, 

 turning rapidly on its own axis. If no 

 host is found the animal may perish. 

 although some have been known to live 

 in water for a long time. \\ hen a fish- 



