The eyes of all insects are immoveable, and have neither iris nor pupil nor eyelids to cover them: but this apparent defect is amply made up to them in a variety of ways: in the case before us, by the complex structure of the organs. +Reaumur+ performed an experiment similar to that which I have just related of +Leewenhoeck+, and with a like result, +Hooke+ computed the lenses in the eye of a horse-fly to amount to nearly 7000. +Leewenhoeck+ found more than 12,000 in that of a dragon-fly; and 17,325 have been counted in the eye of a butterfly. The lenses are most numerous in the beetle, and so small as not to be easily discoverable under a pocket microscope, except the eye be turned white by long keeping. The peculiar construction of the bee's eye, for seeing objects best at a moderate distance, will account for the circumstance noticed by +Wildman+, and also for the following observation of +Dr. Evans+. "We frequently observe bees flying straight homewards through the trackless air, as if in full view of the hive, then running their heads against it, and seeming to _feel_ their way to the door with their antennæ, as if totally blind." +Sir C. S. Mackenzie+ remarked the imperfect vision of bees, and how very much puzzled they are to find the entrances to their hives, if the relative position of the entrances be altered, or the hives be removed two or three yards from the place where they have usually stood. In cases of removal, the bees do not during the first day fly to a distance, nor till they have visited and recognized neighbouring objects. +Mr. Rogers+, in his "Pleasures of Memory," has noticed this defective vision in the bee. Having spoken of her excursive flights to a distance, and referred to her bending her course homewards again, he observes, "That eye so finely wrought. Beyond the search of sense, the soar of thought. Now vainly asks the scenes she left behind; Its orb so full, its vision so confined!" And he concludes that it is by the aid of memory that she retraces her passage back to the hive, by recognizing the scents of the various flowers which she has passed or visited on her outward journey,-- "The varied scents that charm'd her as she flew." But this idea, as Messrs. Kirby and Spence have observed, is more poetical than accurate, the bees being always accustomed to fly to their hives in right lines. In consequence of this peculiarity of insect vision, many of those bees that return homewards after dusk in the evening, are obliged to lie abroad all night. The same peculiarity, added to the acuteness of their smell, has given birth to various contrivances for inducing bees of different hives to mingle peaceably together, as mentioned at page 154.