INFUSORIA. 137 



None of these creatures can be preserved as perma- 

 nently mounted objects. Many chemical solutions and 

 mixtures have been recommended for killing and keep- 

 ing them, but none are satisfactory, the soft bodies go- 

 ing to pieces and melting away almost as soon as after a 

 natural death. If the beginner is very much annoyed by 

 the incessant movements of the free-swimming kinds, 

 and he desires to see how they look when quiet for a 

 moment, the following solution will help. It answers 

 the purpose well in some cases, while in others it is 

 worthless. It always kills, but does not always preserve 

 after death. It is used by allowing a small drop to run. 

 under the cover-glass and to mingle with the drop of 

 water containing the Infusoria. Any druggist can make 

 it, but caution him to use not more than half a drachm 

 (half a teaspoonf ul) of water, or you will be terrified by 

 his bill. If this small quantity is made it is not expen- 

 sive. 



To the half drachm of water add as much iodide of 

 potassium as it can be made to dissolve, and to this so- 

 lution add as much iodine as the .solution can be forced 

 to dissolve. This ends the druggist's part. It only re- 

 mains for you to add enough of the mixture to clean 

 water to make the color a rather deep amber. The 

 proper strength can be learned by experiment. If it 

 kills, and then destroys too quickly, add more water ; if 

 it does not kill quickly enough, drop in a little more of 

 the iodine mixture. 



A weak solution in water of the^r-chloride of iron 



