306 DOMESTICATED TROUT. 



32. Keep very young trout fry in pure filtered spring 

 water, and note how long they remain healthy without the 

 addition of earth. 



33. After the fish in the last experiment begin to sicken, 

 apply earth plentifully, and note the improvement. 



34. Keep 100 young fry in a small box, and 100 in a 

 pond, for six months ; compare the mortality and growth. 



35. Feed two similar lots of young fry, one wholly on 

 curd, the other wholly on liver, and compare results. 



36. Feed young trout fry plentifully on the young of 

 other fish, as suckers, perch, and shiners, and note the 

 result. 



'^']. Take young trout fry that are attacked by animal 

 parasites, and give them a salt bath, as described on 

 page 258, and note the result. 



38. Observe the effect of the parasites on young fry not 

 subjected to the salt bath. 



Ex'Periineiits with Large Trout. 



39. Count the number of respirations of large trout at a 

 temperature of 36°, 45°, 70°, and 80°, and compare the 

 results. 



40. Freeze large trout carefully, but stop the freezing 

 before the body becomes stiff. Thaw out gradually, and 

 note the result. 



41. Let a large trout become motionless from suffoca- 

 tion in still water, then try the effect of vigorous aeration 

 of the water in restoring him. 



42. Ring a bell and make loud noises near trout where 

 you can see them and they cannot see you, and note 

 whether they appear to hear the sounds. 



43. Feed one lot of trout wholly on minnows for three 

 months, and a similar lot on worms, a third lot on meat, 

 a fourth lot on all three, and compare results. 



44. Subject a fish attacked by fungus to the salt bath 

 described on page 258, and note the result. 



