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 be 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 

 lower 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 

 rather 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- 



