MOUNTING WITHOUT PRESSURE. 3O3 



should be so arranged. In these cases very small but wide- 

 mouthed bottles are conveniences, watch-glasses, small 

 beakers, and stemless or footless wine-glasses will always 

 come in useful during these operations; it should be the 

 aim of the student to be cleanly in his manipulations, and 

 endeavour to procure the best results with the minimum 

 expenditure of material. 



Mounting insects without pressure has been much prac- 

 tised of late, and the splendid preparations of Mr. F. Knock 

 cannot be passed by unnoticed. A method of doing this 

 may be found as follows : Let us take the head of the 

 Dytiscus marginalis. Soak it for two days in equal parts 

 of spirits of wine and water, after which transfer it to 

 absolute alcohol for two or three days longer ; now transfer 

 it to turpentine and place it in the light until fairly bleached, 

 take it out of the turpentine and place in benzol until all 

 the former has been eliminated. Now choose a cell just 

 deep enough to hold it, glass or pure tin preferred (by no 

 means must it be of brass, this metal being acted upon 

 by balsam), rinse it out quickly with benzol, insert the head 

 and pour in some balsam just rendered thin enough to run, 

 with benzol, until the cell is full, now put on the cover, 

 cleanse the edge of the cover with a brush dipped in benzol 

 or spirits of wine, and set aside in a warm place that the 

 benzol may escape and become hardened round the edge of 

 the cover. When fairly dry give a good coat of guaiacum 

 varnish (see Recipes), and when this is dry repeat the 

 coating. Finally finish the slide with a ring of asphalte, 

 or black guaiacum varnish. 



MOUNTING IN AQUEOUS MEDIA. This style of mount- 

 ing comprises the fluids and semi-fluids or viscid media ; 

 perhaps the latter are the easier done, but for sake of order 

 an illustration of how to mount starches in carbolised water 

 (see Recipes) will teach the method. 



