OF MICROSCOPIC OBJECTS. 91 



The antennae of insects have been before noticed as being very 

 beautiful when mounted in balsam. This is readily accomplished 

 when they are large ; but those of the most minute insects are 

 much more difficult to deal with, and are less liable to injury when 

 put up in fluid. Goadby^s Fluid serves this purpose very well"; 

 but, of course, the object must be thoroughly steeped in the liquid 

 before it is mounted, for a longer or shorter time according to the 

 thickness. 



The eggs of insects afford some worthy objects for the microscope, 

 amongst which may be mentioned those of the common cabbage 

 butterflies (small and great), the meadow-brown, the puss-moth, 

 the tortoiseshell butterfly, the bug, the cow-dung fly, &c. These, 

 however, shrivel up on becoming dry, and must, therefore, be pre- 

 served in some of the fluids before mentioned. To accomplish 

 this no particular directions are required ; but the soaking in the 

 liquid about to be employed, &c., must be attended to as with 

 other objects. 



Glycerine may be advantageously used for the preservation of. 

 various insects. These should first be cleaned with alcohol to get 

 rid of all extraneous matter, and then, after soaking in glycerine, 

 be mounted with it like other objects. This liquid may also be 

 used for the Entomostraca, which offer a wide field for study. 

 They are to be found abundantly in ponds of stagnant water, &c. 

 Some insects, such as May-flies, &c., are, however, often preserved 

 by immersion in a solution of one part of chloride of calcium in 

 three or four parts of water ; but this has not been recommended 

 amongst the " preservative liquids," as the colour, which is often 

 an attractive quality of this class of objects, is thereby destroyed. 



We have now noticed the treatment which must be applied to 

 those objects which are to be preserved in liquids and cells. We 

 may here state that all slides of this kind should be examined at 

 short intervals, as they will be found now and then to require 

 another coating of varnish round the edge of the thin glass cover 

 to prevent all danger of leakage. The use of the air-pump, in the 

 first instance (as before recommended), and this precaution as to 

 the varnish, will render the 4ides less liable to leakage and air- 

 bubbles, which so very frequently render them almost worthless. 



