162 GOLDFISH VAEIETIES A^D 



rounding a mouth. The shape varies so amazingly that an accurate 

 description is impossible. The two figures shown in Figure 113 are of the 

 same individual. When alarmed the tentacles are entirely withdrawn, 

 making recognition still more difficult. 



They rapidly deplete an aquarium of daphnia and newly hatched 

 fishes. When a school of fry under 5-16 inch long is disappearing with- 

 out apparent cause, it will be well to take a sharp look for some harmless 

 looking hydra. 



Hydra possess a poison which quickly stupifies their prey, and to fish 

 large enough to eat the hydra this poison doubtless has an unpleasant 

 taste. There is no fish known which will eat them. To get rid of this 

 pest, remove all fish, snails, etc., from the tank and place in it a solution 

 of permanganate of potassium of a strength of 3 grains to the gallon of 

 aquarium water. Allow this to stand for two days, change water and 

 replace fish. This treatment will not kill plants. 



H no small living food be placed in the aquarium, hydra will in a 

 few weeks be starved. 



One experimenter has claimed that by raising the water temperature 

 to 110° Fahrenheit for a few minutes the hydra will all be killed, while 

 the plants will not be affected. 



LARGER ENEMIES OF FISHES 



It should not be understood that the foregoing are the only serious 

 enemies of pet fishes. In the greenhouse, outdoor pool, or even the 

 library, misfortune is liable to descend in various guises. Chief among 

 these are the cat, rat, muskrat, snake, heron, kingfisher and small boy. 

 Fishes are also taken by the large frog, sandpiper, horned owl, crayfish, 

 and blackbird. The latter specializes on picking out the eyes of telescope 

 fishes if the water is near enough to the edge of tank for him to reach 

 them. 



