We have seen that human albinos are anosmic, and the same is probably true of animal albinos. But care is necessary in making observations on suspected albinos in animals, as even when they are altogether white a certain amount of black pigment remains about the face and nose. The following reports, however, would lead us to conclude that as with man, so with the animals, a relative deficiency of pigment is associated with a dull olfactory sense. It is by smell that the herbivora detect and avoid plants which are poisonous, and when poisoning does occur, it is usually a white animal that suffers. In some parts of Virginia the farmers will only rear black pigs, because, they say, the white ones eat and are poisoned by the roots of _Lachtanthus tinctoria_. For the same reason in the Tarentino only black sheep are reared. Thirdly, the dark-skinned human races have a keener sense of smell than the lighter races. Fourthly, the sense grows more acute as we get older, as we have already seen, and nasal pigmentation, it is said, also increases with age. As to the function of the olfactory pigment, Ogle remarks first of all that odours are absorbed more readily by dark than by light materials. Pigment is also present in the labyrinth of the ear as well as in the eye, and its presence in these organs seems to be essential to their activity. It is to be noted that the pigment does not occur on the nerve structure in any of those end-organs, but external, though contiguous to it. In the eye, it lies in contact with the rods and cones of the retina; in the nose, with the olfactory hairs; in the ear, with the terminal bodies of the auditory nerve. Hence the pigment, he supposes, must be associated with the reception of the sensory impressions. In the eye and the ear those impressions are undulatory in character. That being so, he holds that the undulatory theory of olfaction also is probably the correct one. Ogle finishes with the remark that the theory would be strengthened if it could be shown that pigment was specially suited for the absorption and modification of undulations. It is interesting to us to learn that claims are now being made that pigment does possess the power necessitated by Ogle’s theory. At all events, there is a theory of vision (Castelli’s) which claims for the ocular pigment the power of absorbing and modifying light waves, and Heyninx holds that the olfactory pigment possesses a similar property.