150 GENERAL BIOLOGY 



water to just cover them and add a few drops of alcohol 

 every few minutes. After several hours they will be found 

 to be motionless and should not respond to tactile stimuli. 

 They should now be laid out straight and flat in a disk of 

 weak alcohol and allowed to remain for not more than four 

 hours. They are then to be placed in 80 per cent alcohol, 

 or better a mixture of alcohol and 10 per cent formalin for 

 preservation. The worms should be kept straight in the 

 preservative since they are much easier to study when in 

 this condition. 



A somewhat clearer demonstration of setae and of external 

 openings can be made on worms killed (after narcotizing) 

 in 1 per cent chromic acid. After twenty-four hours in the 

 chromic acid, wash overnight in water and preserve in 

 alcohol. These are not so good for internal study. 



For sectioning place worms in a dish with moist filter 

 paper and leave for several days until they void clean filter 

 paper instead of dirt. The digestive tract is now in con- 

 dition for sectioning. Narcotize with alcohol (or chloral 

 hydrate, or chloretone) and when motionless cut into small 

 pieces and fix in Bouin's fluid. 



It is very easy to keep earthworms alive all winter with 

 little or no trouble. In a wooden box filled with moist 

 loamy soil place a number of worms and keep the box in 

 a cool place. Every few days leaves, pieces of apple, etc., 

 should be spread on the surface for the worms to feed upon. 

 Cover the box with a heavy cloth (burlap) which is kept 

 moist and the soil will need very little attention. If the 

 soil should appear dry it must be sprinkled enough to 

 thoroughly moisten it. 



Grasshopper. The larger grasshoppers are best for study 

 on account of their size, and are necessary if much internal 

 study is to be made. But for the study of external features 



