Preparing and Mounting Entomological Specimens 195 



object has to be retained in the centre of the cell by slight 

 pressure on the part of the cover-glass. When the cell is 

 quite dry, apply a coat of shellac cement to its upper 

 surface, and let it nearly dry ; then take a brush and some 

 clean water and moisten the inside of the cell. This is 

 done to prevent the formation of air-bubbles, for if glycerine 

 is put into a dry cell, bubbles are sure to give a lot of 

 trouble. Now fill the cell' with glycerine and put in 

 the specimen, which should be previously soaked in dilute 

 glycerine for an hour or two, and with a needle place it in 

 the desired position ; apply the cover-glass very carefully, 

 so that no air-bubbles may be enclosed, and let it settle 

 down by its own weight until it rests on the surface of the 

 cell ; then press it down with a needle-point until securely 

 embedded in the half-dried cement, and set aside for an 

 hour or two to dry. The exuded glycerine may then be 

 washed away by holding the slide under a water-tap. When 

 all trace of glycerine is removed, dry the slide with a soft 

 cloth, and apply a coat of black shellac enamel. 



Heads of large insects may be secured in the centre of 

 the cell in the following way : Take a fine needle, thread 

 it with a hair, and run ifc through the specimen. Un- 

 thread the needle, take up each end of the hair with the 

 object suspended and stretch it across the cell so that it 

 may be embedded in the cement on each side. Now apply 

 a cover-glass, press it down until securely fixed, and if 

 the specimen is not in the middle of the cell, adjust it by 

 pulling on the hair on one side. Put away to dry, cut off the 

 ends of the hair close to the edge of the cell, wash away 

 excess of glycerine, dry, and apply a coat of shellac enamel. 



PRESERVING AND MOUNTING ROTIFERA.* 



Published by kind permission of Mr. C. F. Rousselet, 

 Hon. Curator F.R.M.S. 



There are few observers of pond life who have not felt 

 a keen desire to preserve and keep these small highly- 



* Reprinted from Knowledge. 



132 



