APPENDIX 219 



and should be handled with extreme care. It would be well 

 to memorize the following cautions and try to lise them until 

 they beconie habitual : 



Never touch the lens of the eyepiece or objective with 

 the hand. Cleanse them with a camel's-hair brush or a 

 piece of soft silk. 



Never move the lens downward while the eye is at the 

 eyepiece, always focus upward, especially if you are using 

 the coarse adjustment. 



Before leaving a microscope, rub it dry and clean it with 

 a piece of flannel or chamois skin and put it in its proper 

 place. Never leave a microscope in the direct rays of the 

 sun or where dust may gather on it. 



II. HOW TO USE THE TABLES OF CLASSIFICATION. 



To a student who has not used the Tables of Classifica- 

 tion, the following suggestions may be found helpful. It 

 will be easier to tjace to its family the type specimen 

 which has been thoroughly studied as its characteristics are 

 fresh in the mind. 



Some of the tables have the different divisions in figures, 

 and some have letters. The difference between these will 

 be apparent at a glance. 



These tables do not carry the classification further than 

 the families; classification into genera and species can be 

 made by consulting specialists on the different classes of 

 animals. 



Suppose that we have a beetle which we desire to trace 

 to its proper family. We proceed as follows: 



