Page:The Zoologist, 4th series, vol 5 (1901).djvu/357

Rh invariably selects and visits a flower of one particular colour, we can only record the observation, but certainly not assume that what we see as white is seen by them in the same hue. Mr. J.A. Harvie-Brown has protested against the assumption "that the colour of insects, as seen by us, is comparable with what may be seen by fish. Fish see though a different medium from ours, and surely we see differently through theirs." Prof. Plateau, an authority on the physiology of Arthropods, a few years ago published a series of memoirs giving the results of his experiments in endeavouring to ascertain the actual powers of vision possessed by insects and other Arthropods. Dr. Sharp, of Cambridge, has placed us all under an obligation by giving a condensed account of these observations, and also a critical summary of results. He gives his general impressions as derived from Plateau's experiments as follows:—

"1. Insects in motion are guided largely by the direction of light, and the existence of lights and shades. That when walking they are guided by a combination of light-impressions, with specific habit (that is, going upwards or downwards, towards the light, or away from the light), and by tactile impressions; these latter not acting when the insect is in flight.

"2. That there is at present no evidence at all that the light perceptions are sufficiently complex to be entitled to be called seeing; but that, as the large development of the compound eye permits the simultaneous perception of movement, its direction, and of lights and shades over a certain area, a Dragonfly may pursue and capture another insect without seeing it in our sense of the word seeing."

Before leaving this section of our subject, and to make clear our suggestion that little can be justly predicated as to sight preferences or warnings by insects, we may again quote Mr. G.