226 THE SCOTTISH NATURALIST 



AVhile keeping the slide warm, gently move the cover by pressure 

 with a blunt needle point, thus causing the front legs to 

 expand. Of course this must be done under a lens. 



A simple way of keeping a slide warm in the absence of 

 a hot metal plate is to fill an ordinary 6 or 8 oz. medicine 

 bottle with hot water, and lay it on its broad side with the 

 slide upon it. The hot water may be tinted if desired. 

 I mounted some Hcematopinus macrocepliahis in glycerine 

 jelly, because I thought that it showed up the tracheal 

 system rather better than was the case with balsam ; but 

 I found it necessary to employ the following rather elaborate 

 method, 1 because the specimens proved apt to be crushed by 

 sudden transference from water to glycerine jelly : 



Boil in KOH 5 per cent, for twenty minutes. 



Wash in distilled water. 



Substitute 50 per cent, alcohol and leave for twenty minutes. 



Increase the alcohol to 70 per cent, and leave for ten minutes. 



Substitute 70 per cent, alcohol containing 5 per cent, glycerine. 

 (The glycerine and water may be warmed to dissolve the 

 glycerine before the alcohol is added.) Leave the Hremato- 

 pinus in this for six hours in a closed vessel. 



Substitute 10 per cent, glycerine in 70 per cent, alcohol, and 

 leave for six hours or longer. 



Substitute 20 per cent, glycerine in 70 per cent, alcohol, and, 

 after six hours, remove the cover of the vessel and allow the 

 alcohol to evaporate, precautions being taken to protect 

 the vessel meantime from dust. 



Mount on a plain slide in glycerine jelly. 



Press lightly with a blunt needle on the cover-glass, above the 

 head or front thorax, making a tremulous movement. The 

 claws will turn outwards. Pressure on the abdomen is apt 

 to cause more or less distortion. 



It is sometimes advisable to use Farrant's' solution as 

 a substitute for glycerine* jelly, as it allows of more delibera- 

 tion in the laying out of delicate objects. For example, 

 I have some successful mounts of Aphides, in which the 



1 Adapted from directions in Stephen and Christopher's Practical 

 Study of Malaria. 



