In the centre of Plate VI. may be seen the front view of the head of a bee, showing both kinds of eyes, three simple eyes arranged triangularly in the centre, and two large masses, compound eyes, at the sides. The simple eyes, termed “ocelli,” are from one to three in number, and usually arranged in a triangular form between the two compound eyes. Externally they look merely like shining rounded projections, and can be seen to great advantage in the dragon-flies. The compound eyes may be considered as aggregations of simple eyes, set closely together, and each assuming a more or less perfect six-sided form. Their number varies very greatly; in some insects, such as the common fly, there are about four thousand of these simple eyes in one compound one, in the ant only fifty, in the dragon-fly about twelve thousand, and in one of the beetles more than twenty-five thousand. Fig. 18 shows a portion of the compound eye of the Atalanta butterfly, and Fig. 20 the same organ of the death’s-head moth. A number of the protecting hairs may be seen still adhering to the eye of the butterfly. Fig. 22 is a remarkably good specimen of the eye of a fly (_Helióphilus_), showing the facets, nearly square, the tubes to which they are attached, and portions of the optic nerves. Fig. 23 is part of the compound eye of a lobster, showing the facets quite square. All these drawings were taken by the camera lucida from my own preparations, so that I can answer for their authenticity. On Plate VIII. Figs. 6 and 12, the reader will find two more examples of eyes, these being taken from the spiders. Fig. 6 is an example of the eight eyes of the well-known zebra spider, so common on our garden walls and similar situations, hunting incessantly after flies and other prey, and capturing them by a sudden pounce. The eyes are like the ocelli of insects, and are simple in their construction. The number, arrangement, and situation of the eyes is extremely varied in spiders, and serves as one of the readiest modes of distinguishing the species. Fig. 12, Plate VIII., represents one of the curious eyes of the common harvest spider, perched on a prominence or “watch-tower” (as it has been aptly named), for the purpose of enabling the creature to take a more comprehensive view of surrounding objects. * * * * *