106 PREPARATION AND MOUNTING 
This method of preparing and mounting insects I car 
strongly recommend as giving first-rate results; but where 
the specimens are small, they seldom need the soaking in 
caustic potash which larger ones must have. It is only 
necessary to leave them awhile in turpentine, especially 
when they have been first dried with gentle pressure between 
two glasses, and then mount with balsam-in the ordinary 
way. With many, even of the larger insects, by soaking 
them in turpentine or oil of cloves for a longer time, they | 
are made so much more transparent and even colourless, 
as to exhibit their internal organs (which are visible in 
layers, by the aid of the binocular microscope), the muscles 
of the legs, &c. They become also very beautiful objects for 
the polariscope. 
Amongst the insect tribes there is abundant employment, 
especially for the lower powers of the microscope. But if - 
the deeper wonders and beauties of the animal economy 
are to be sought out and studied, it is desirable that the 
various parts should be set separately, in order that they 
may receive 2 more undivided attention, as well as be ren- 
dered capable of being dealt with under the higher powers. 
We will therefore briefly consider the treatment which the 
different portions require. 
The eyes of butterflies, and indeed of almost all insects, 
afford materials for a study which is complete in itself. 
When examined with a tolerably high power, instead of 
finding each eye with an unbroken spherical surface, it is 
seen that many are composed of thousands of hexagonal 
divisions, each being the outer surface of a separate portion 
termed the ocellus. In others these divisions are square; 
but in all there is a layer of dark pigment surrounding their 
lower parts. The ocelli may be partly removed from the 
eye, which will show how their tapering forms are arranged. . 
But here we have to consider how to place them in balsam 
for preservation. The eye being removed from the insect, 
and the dark pigment removed hy the use of a camel-hair 
pencil, must be allowed to remain in turpentine at least for 
