Some Lemuroids have short, and others have long muzzles, and there is great variety in the shape of the head. Evidently those with long noses have a very fine sense of smelling, and the whole of the members of the sub-order have a peculiar twist in the outside nostril, which distinguishes them from the Monkeys of both the Old and the New World. This twist was thought to be of great importance in classifying the Lemuroida in the animal scale, and they are often at the present day termed “Strepsirhini,” from the Greek words which mean curved nostril. Some scent out insects and grubs under the bark of trees, and all use this sense in searching for food by night. There are some long hairs about the upper lip and cheeks like those of a Cat, and these “smellers” are doubtless extremely sensitive to touch, and although they do not assist the sense of smelling, they help the animals in avoiding danger in their movements through the dark underwood. The colour of the iris (the membrane around the pupil of the eyes) is very beautiful in most, and as the eye is large and staring, it is well seen. Sometimes the pupil is round, but in some kinds it is a slit, as it is in the domestic Cat, for instance, and this shape has much to do with their nocturnal habits. The iris moves in two directions, and makes the pupil either larger or smaller; and the importance of this gift is, that whilst a small pupil admits only a very slight quantity of light into the body of the eye, a large one allows a great amount to enter; hence, at eventide the pupil dilates, or, in other words, the iris acts so as to enlarge it, and all the light possible enters, but in sunlight the pupil contracts, even to a point, the iris moving so as to shut out the superfluous and injurious illumination. The nocturnal kinds require a very dilatable pupil, for they move often in comparative darkness, and when the least ray of light is of benefit to them. Besides this structure, there is another which has to do with husbanding, and making the most of faint light. If the eyes of a Lemur are examined a little carefully, they will be found to glare with a very metallic lustre in certain lights, just as those of a Dog and Cat. It appears that in certain animals, and in the Lemuroids, there is a peculiar layer within the eye which looks coloured; but really it is only very finely marked by fibres, which decompose the common white light into its primitive colours, in the same manner as the extremely delicate markings invisible to the naked eye on mother-of-pearl produce the well-known beautifully iridescent tints. This layer is behind the sensitive layer of the eye, and it acts as a concave reflector, collecting the slightest glimmers, and making them of use. The membrane is called the tapetum. It has been noticed that there is a difference in the expression of the eyes of the Lemuroids and Monkeys, and certainly these last have the advantage of showing their impudence,