INSECTS. 
151 
lenses aggregated together upon the same optic nerve. 
The microscope reveals to us that the compound eye of 
an Ant contains fifty lenses ■, that of a Fly, four thousand ; 
that of a Dragon-fly, twelve thousand ; that of a Butterfly, 
seventeen thousand ; and that of a species of Mordella (a 
kind of beetle), the amazing number of twenty-five thou- 
sand. Every one of these regular, polished, and many- 
sided lenses, is the external surface of a distinct eye, fur- 
nished with its own iris, and pupil, and a perfect ner- 
vous apparatus. It will thus he seen that each hexagonal 
facet forms a transparent horny lens, immediately behind 
which is a layer of pigment diminishing to a point in the 
centre, where it forms a pupil • that behind this a long 
six-sided prism, answering to the crystalline and vitreous 
humours in the human eye, extends, diminishing to its 
lover extremity, where it rests upon the retina, or net- 
work expansion of the optic nerve. Some of the minuter 
details of this exquisite organisation are still matters of 
conflicting opinion ; but these we omit, as our purpose is 
ra ,ther to convey to our readers a general idea of the 
structure of this complex organ of vision. “ This also 
cometh forth from the Lord of Hosts, which is wonderful 
in counsel and excellent in working.” (Isa. xxviii. 29.) 
With very few exceptions, the animals of the previous 
Classes are confined to the waters ; the density of such a 
medium being requisite for the support of their soft and 
feeble bodies. But the solid external investiture of 
Insects, and their well-jointed limbs, impart to them suffi- 
cient firmness and precision of motion to range the earth 
and air ; many species being endowed with organs which 
enable them to swim, run, or fly at their pleasure. Pro- 
