VISION IN INSECTS. 123 



the practice of bees flying, as Huber has stated, 

 straight to and from the hive, we have in numerous 

 instances seen a bee search the same blossom two or 

 three times in the course of a few minutes, in utter 

 forgetfulness of having already plundered it of its 

 honey *. 



If Reaumur, however, be correct in his opinion, 

 as we are inclined to think he is, these apparent dis- 

 crepancies may be easily reconciled ; for he attempts 

 to show, that bees and most other insects are en- 

 dowed with two sorts of eyes, one for distant, and 

 another for near vision; instead of having the power 

 as we have of adapting the eye to various distances, 

 the nature of which adaptation is not well under- 

 stood f. In order to understand this more precisely, 

 it will be necessary to enter into a few details as to 

 the number and structure of the eyes of insects. 



It may at first appear riot a little puzzling to con- 

 ceive how a spider with eight eyes, a centipede with 

 twenty, and a butterfly with thirty-five thousand 

 facets in its two eyes, can perceive only one object ; 

 yet the difficulty is not of a very different kind from 

 that of our own two eyes representing only a single 

 object and not two, a subject which has exercised the 

 ingenuity of many a philosopher. Vandermonde J, 

 for example, supposed that children at first see 

 double, and correct the error by experience ; an 

 opinion adopted by Blumenbach : Dr. Reid referred 

 it to an original and inexplicable law of human na- 

 ture , confessing thereby his inability to explain it ; 

 and some of the old philosophers satisfied themselves 

 that it was because the nerve from each eye meets 



* J. R. 



t Des Cartes, Mariotte, Juriue, Dr. T. Young, Mr.C. Bell, Mr. 

 Travers, &c. have given various opinions on this subject. 

 I Apud Haller, Physiol. 

 Inquiry into the Human Mincb 



