In addition to these "facetted" eyes, bees have, on the top of the head, three simple ones, called by some writers "coronets," by others "stemmata." Their position and arrangement are shown at _g_ in Fig. 27, p. 98. The focal length of their lens is said to be short, and they are supplied with numerous filaments from the optic ganglia. The special purpose of these simple organs is not well ascertained. If their focal length is short, this would seem to imply that their range of vision is also very limited. But it is very possible they may possess a focusing power, which would adapt them for seeing at all distances. Réaumur thinks they may, with their hemispherical lens, act as microscopes. This point needs further investigation, as the subject of the uses of these two kinds of visual apparatus is, at present, very far from satisfactorily elucidated. One remarkable fact relating to the "stemmata" must be mentioned. It is that, if they be covered with a little opaque paint, the bee, on being let go, will fly continually upwards. Dr. W. B. Carpenter considers this curious fact due to automatic movements initiated by the ganglia connected with flight, uncontrolled by the visual impressions which the simple eyes convey in their natural condition. Neither kind of eye has a lid, but both are protected from dust by numerous small hairs growing round them, and in the points of junction of the facets. How far the eyes of bees enable them to distinguish colours is still a moot point. On _a priori_ grounds we should expect that one very definite object in the hues of flowers is to attract the notice of insects, just as we have strong reason to believe that odours exhaled in the vegetable world serve this purpose. Sir John Lubbock has detailed a series of experiments on this point, the following summary of which is abstracted from his work on _Ants, Bees, and Wasps_. He says, p. 304: "In recording the results I marked down successively the order in which the bee went to the different-coloured glasses (on which honey was placed). For instance, in the first journey from the nest, as recorded below, the bee lit first on the blue, which accordingly I marked I; when the blue was removed, she flew about a little, and then lit on the white; when the white was removed she settled on the green; and so on successively on the orange, yellow, plain, and red. I repeated the experiment a hundred times, using two different hives one in Kent, and one in Middlesex and spreading the observations over some time, so as to experiment with different bees, and under varied circumstances. Adding the numbers together, it, of course, follows that the greater the preference shown for each colour, the lower will be the number standing against it. "The following table gives the first day's observations _in extenso_:--