The skin is smooth and shiny, so smooth and so shiny that it has often been compared to coach leather. But nevertheless they are not entirely without that most essential character of the class Mammalia, a coating of hair. The hairy covering is, however, reduced to the very smallest proportions; it is represented {342} by a few hairs only--so few that they can be counted with ease--in the neighbourhood of the muzzle. These hairs are not present in all Whales; they are absent, for example, in the White Whale or Beluga. When present they are not furnished either with sebaceous glands or with muscular fibres, which are such universal concomitants of the hair follicles in the Mammalia generally. This appears to be conclusive evidence that the hairs, few as they are, are still undergoing degeneration. The need for a furry coat is removed by the presence of a thick coating of fat immediately underlying the skin. This is known as the blubber, and is the main incentive to the pursuit of Whales. It must not, however, be assumed without further argument that the hair is absent because its place is taken, as a mechanism for retaining the heat, by the blubber; for the Seal tribe possess both fur and blubber. Another conceivable explanation is quite at variance with such a view of economy. It may be noticed that among Ungulates there is a tendency to lose hair, particularly among more or less aquatic forms. Thus the Hippopotamus is almost naked (as is indeed the Walrus); the Rhinoceros, too, often a frequenter of marshy soil, is almost as denuded as is the Hippopotamus. It is not, however, settled that the Whales have anything to do with the Ungulata; otherwise an additional argument might be used, that is, the secular loss of hair in some members of this group. The Hairy Rhinoceros, _Rh. tichorhinus_, was, as its name denotes, a hairy beast; the Mammoth was equally so. The descendants, or at least the modern representatives of both these creatures, are but scantily clad with hairs. A final reason for the naked character of the skin in existing Cetacea is closely connected with a feature in the organisation of three or four living species which must first be described.