vMlC-R OS COPICAL ESS A TS. 



are furnifhed with a collection of an indefinite number of very 

 final 1 iiirgle eyes, placed in one common cafe or focket. 



The two protuberances on the head, which are formed by 

 this -congeries of eyes, feem to the naked eye to confift of a num- 

 ber of lines, croffing with great regularity andexactnefs, at fome 

 little diftance from each other, like the mefhes of a net, from 

 whence they have been termed the reticular eyes. Thoie of the 

 libellula are peculiarly well adapted, on account of their fize, for 

 a microfcopie view of this fubjecl. Thefe eyes are fo perfectly 

 fmooth and polifhed, that when viewed as an opake objeft, they 

 will, Like fo many mirrors, reflect the images of all the furround- 

 ing objects. The figure of a candle may be feen multiplied 

 almoft to infinity on their, furfaces, fhifting it's beam to each eye 

 according to the motion given it by the obferver's hands. Other 

 animals are obliged to turn their eyes towards any object, but 

 thefe have eyes ready directed to it, on whatever fide it may pre- 

 fent itfelf. The genus of cancri have their eyes moveable, but 

 ibr the molt part reticulated dike other infects. 



Though the reticulated eyes of flies are large, not only in pro- 

 portion to the fize of the creature, butabfolutely and in themfelves ; 

 yet thefeveral fmall eyes> of which they are compofed, are re- 

 markably minute in companion of thole of the butterfly clafs. 



Moft of the butterfly -clafs have in each of their reticulated 

 eyes many thoufand fmall ones ; but the fly ektfs greatly exceed 

 them in the number of thefe, as many of their eyes are three times 

 as large as thoie of the butterfly, and befides that each fmaller eye 



•is vafily more minute. 



