89 



used with advantao'e for killing aud fixation. Whichever 

 reagents are used, the specimens shouhd be afterwards 

 placed in 90 per cent, alcohol, to which have been added 

 about five drops of potassium livpochlorite (concentrated 

 solution j to each fiuid ounce of the alcohol. After 

 remaining in this for about half an hour, they sliould be 

 washed in fresh alcohol of similar strength and then 

 passed into absolute alcohol. The potassium hypochlorite 

 serves to remove the pigment, and also softens the 

 chitinous parts and aids in section cutting. 



The process of embedding is best performed in watch- 

 glasses, using paraffin of a low-melting point, which is 

 afterwards replaced by hard paraffin for cutting. For 

 staining, the best results were obtained by using 

 Manns methyl-blue-eosin and Heidenhains iron-alum 

 hsematoxylin. All staining was done on the slide by 

 prolonged treatment, and afterwards washed out to the 

 required degree of colouration. 



The eggs were killed and fixed in both hot water and 

 hot TO per cent, alcohol, and afterwards kept in 90 per 

 cent, alcohol for five weeks for hardening purposes. After 

 this treatment, the egg membranes can be dissected away 

 from the embryos with the aid of a pair of fine needles 

 under a low-power microscope. The embryos can then be 

 stained with borax carmine, and mounted whole 

 in glycerine for examination. For instructions as to 

 sectioning the eggs, vide Folsom (10). 



