VISION IN INSECTS. 



13i 



cause has ceased, prolonging the sensation of hght 

 (especially of a vivid one) for an instant in the eye. 

 We may thus conceive the possibility of other animals, 

 such as insects, incapable of being affected with any 

 of our colours, and receiving their whole stock of lum- 

 inous impressions from a class of vibrations altogether 

 beyond our limits, as Dr Wollaston has ingeniously 

 imagined (we may almost say proved) to be the case 

 with their perceptions of sound. '"^ 



This view of the matter is certainly beautiful and 

 plausible, though, yi the present state of our knowledge, 

 we can only admit it as a theory. 



The vision of insects has been recently investi- 

 gated with great minuteness by Professor Miiller, of 

 Bonn,| an excellent account of whose researches 

 has been given by Mr Parsons, of which we shall 

 avail ourselves. * The compound eye of the com- 

 mon or grey dragon fly ' [Libellula Vidgata), says 

 Mr Parsons, ' when examined externally, may be 

 divided into two parts ; one superior and posterior, 

 of an obscure red colour, and provided with facets 



* Encycl. Metropol., Art. Light. 

 t Act. Cur. Bonn ; and Meikel's Archiv. 1829. 

 VOL. XII. 12 



