98 THE LARVA OF THE BLOW-FLY. 



by placing the slides for a few moments in an oven at 

 ioo° Fahr. 



Clouds are produced by water or alcohol. A water cloud 

 cannot be removed, and depends on the presence of water in 

 the methylated spirit. Alcohol clouds arise from the use of 

 too much clove oil. Clove oil will not dissolve alcohol, but 

 displaces it. Setting the slide on end usually dissipates any 

 alcohol cloud. 



The specimens must on no account be allowed to dry at any 

 stage of the process ; if they do they are ruined. The greatest 

 danger is after the washing with absolute alcohol. The 

 methylated spirit used must be the best, and entirely free from 

 gum. After draining off the clove oil I mount in Canada 

 balsam dissolved in xylol. 



Staining in bulk before cutting may be effected with borax 

 carmine, but is often unsatisfactory. Picro-carmine may also 

 be used. I find that immersion of the part of the larva to be 

 stained in solution 4 for some hours facilitates the penetration 

 of the stain. In no case can an entire larva be satisfactorily 

 stained, as the integument is practically impervious. 



Whatever process is adopted, no good can result from 

 improperly-fixed tissues. 



