NUMBER OF LENSES IN THE EYE. 



23^ 



that they should not have been recognized in the 

 intermediate locality ! 



A, The Dragon-fly, with its mask extended; b, the same, with the mask 

 closed and discharging a current of water. 



The eyes of the dragon-fly are extremely beautiful, 

 being prominent, and exhibiting an infinity of little 

 hexagonal facets. These were counted by Leeuwen- 

 hoek, and were found, in a single eye, to amount to 

 12,000. Great as this number may appear, it is sur- 

 passed by that exhibited in the eye of some other 

 insects, for 17,325 have been actually reckoned in 

 that of a butterfly. 



I have mentioned that the larv^a of the dragon-fly 

 is an inhabitant of the water. It is in that state 



