INVERTEBRATE ZOOLOGY. 85 



a worm in a saucer of waiter and introduce alcohol very slowly until the de- 

 sired result be obtained. It answers nearly as well and is often more conve- 

 nient to throw them alive into 25-30 ^. They will writhe and coil themselves 

 at first, but ultimately the majority will straighten out quite well. 



b. Preserving. If the specimens are to be used for dissection, the body 

 cavity should be opened bj- a few slits along the mid-dorsal line, and the spec- 

 imen returned to the 30 f; 4-6 hours and then in TO r; for permanent preserva- 

 tion. If immediate dissection is desired, open the animal as soon as killed, 

 dissect under 30 ;, and place in 70 f^ at the end of the first day's work. For 

 staining and sectioning, a more complicated course is necessary. The alimen- 

 tary canal is normally filled with earth, which renders sectioning impossible. 

 To get rid of this, keep a living animal for several days in a box of damp 

 coffee-grounds until the earth is entirely replaced. Fine saw-dust is also 

 used, but is not as good. Fair results may often be obtained by simply starv- 

 ing an earth-worm in clear water, changing it daily. In sections taken from 

 such animals, the cells of the alimentary canal will be abnormallj' contracted. 

 If none of the aliove methods are convenient, very small earth-worms may 

 be used, thus reducing the qi;antit}' of earth to a minimum. When ready, 

 the animal is to be killed as above, but removed as soon as possible, and cut 

 into several pieces, which are to be separately preserved in some good fixative 

 with subsequent treatment with alcohol. Either of the following are espec- 

 ially recommended : — 



I. A(iueous corrosive sublimate 2-6 hours. 



Water : running, or large quantity often changed, '4-3^ h. 



30^' alcohol 4-8 h. 



70 % alcohol — permanently. 



II. Kleinenberg's Picro-sulphuric acid. 2-6 h. 



70;? — This should be changed repeatedly at intervals of 4-12 h.. until it 

 remains colorless. 

 The original location of each piece should be kno-«ni, and may l)e designated 

 by cutting the pieces into different lengths, or by preserving them in separate 

 bottles, carefully labelled. 



62. General Anatomy. 



(a) External characteristics. Notice again on the dead animal the parts 



mentioned in 60. the segments, bristles, cingulum, etc. At the anterior end 



is a partial segment, projecting over the mouth. This is the lyrostomium, or 



lip. and is not counted as a segment. Count the segments from this past the 



7 



