134 PREPARATION AND MOUNTING 
bubbles are formed by the operation. The cover may be 
fixed by the aid of gold-size, Japan, or any of the usual 
varnishes, care being taken, as before, that all the compound 
is removed from the parts to which the varnish is intended 
to adhere. 
The glycerine jelly of Mr. Lawrance, before mentioned, 
requires almost a similar treatment. ‘The objects to be 
mounted in this medium should be immersed for some time 
in a mixture of equal parts of glycerine and dilute alcohol: 
(six of water to one of alcohol). The bottle of glycerine jelly 
must be placed in a cup of hot water until liquefied, when it 
must be used like Canada balsam, except that it requires 
less heat. A ring of asphaltum varnish round the thin glass 
cover completes the mounting.” 
The Infusoria (see Chapter IV.) are sometimes preserved 
in liquid; but present many difficulties to the student. 
Different kinds require different treatment, and consequently 
it is well, when practicable, to mount similar objects in two 
or more liquids. Some are best preserved in a strong 
solution of chloride of calcium, others in Thwaites’ liquid, 
whilst a few keep their colour most perfectly when in 
glycerine alone. ‘There can be little doubt that light is the 
bleaching agent in most cases. Many of them, however, 
are so very transparent that they present but faint objects 
for ordinary observation. For this reason, however, they are 
sometimes dyed in solution of magenta or other colour, as 
elsewhere noticed. The Desmidiaceze require somewhat 
similar treatment, and may be mentioned here. The solution 
of chloride of calcium has been strongly recommended; but 
no preservative liquid seems to be without some action upon 
them. Both of the above classes of objects should be mounted 
in shallow cells, so as to allow as high a microscopic power 
as possible to be used with them. 
ENTOMOSTRACA.—In every ditch or place where vegetable 
matter exists, these little active, jerking pieces of life are 
certain to be found. They are covered with a horny trans- 
parent shell, and are various in form. Mr. Tatem gives the 
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