127 ' 



Hardening. — After killing and fixing and washing the 

 specimens are kept in alcohol of 85^ strength. The speci- 

 mens may be kept thus indefinitely. Specimens which are 

 to be prepared for immediate cutting must now be hardened. 

 (If the specimens are to be stained /;/ toto^ the staining should 

 now be done before removal to the 95^ alcohol. For direc- 

 tions, see p. 137.) Remove the specimens to 95^ alcohol 

 and leave for twenty-four to forty-eight hours, depending 

 upon size of specimen and degree of chitinization of integu- 

 ment. Then remove to absolute alcohol for from twenty- 

 four to forty-eight hours. The specimens, if properly fixed, 

 will now be thoroughly hardened. 



Clearing. — (For theory and practice of clearing, see Lee's 

 Vade-Mecum, p. 64 et seq.) Remove the specimens from ab- 

 solute alcohol to a vial which has been half-filled with xylol 

 and then filled with absolute alcohol. Put the specimens 

 into the vial and leave them for twelve to twenty-four hours. 

 Then remove to a vial filled with xylol and leave them 

 until cleared. This will require from twelve to twenty-four 

 hours. 



We have used cedar-wood oil a great deal for clearing, as 

 follows : Remove the specimens from absolute alcohol to a 

 mixture of absolute alcohol, one part, cedar-wood oil, one 

 part, for twenty-four hours. Then remove to pure cedar- 

 wood oil for twenty-four hours. 



Chloroform, which has been much used, is rather decried by 

 the present-day workers. For insects it should be avoided, 

 as it has little penetrating power. 



Infiltrating with paraffin, and imbedding. — After 

 clearing, the specimens are to be infiltrated with melted 

 paraffin. The specimens should be removed from the vial 

 of cedar-wood oil or xylol into a small dish (watch-glass, 

 beaker, evaporating dish, casserole, tin ^'pattie" dish), into 

 which part of the cedar-wood oil or xylol from the vial is 



