The common _hedgehog_ though a burrowing animal like the _mole_ is not always underground as his distant relative is. He is not always mining and though of ancient lineage he is a “slacker” compared with the mole, hibernating for months, and spending also much time in his nest and prowling slowly about above ground for insects. He has thus acquired his somewhat indifferent epidermis that one finds, but with the addition of sparse papillary ridges. It is the species among this list with the fewest of these tactile structures, for there are but three or four separate ridges on six of the ten digits, and radiating groups on only three of all the palmar and plantar pads. So _quâ_ touch it is ill-equipped, though it has adapted a higher form of tool than the rabbit. The common _squirrel_, that sits much and walks mainly on branches of trees just as much as it needs to do, has an epidermis little differentiated, and one which is corrugated with scanty papillary ridges on the palmar and plantar pads, and none on the digits. The _squirrel-like phalanger_ which flies always more or less downwards by a kind of parachute-arrangement has most of its palmar and plantar skin covered with papillary ridges encroaching upon its corrugated areas, and a response to more delicate tactile experience has been thus produced by its intermittent performance of ordinary progression. _Azara’s opossum_ presents about as large a part of the surface covered with nodules as with papillary ridges, the latter highly-developed for an animal so low, zoologically-speaking, but one in which delicate discrimination is much practised. The _kinkajou_, another arboreal animal which walks about on trees more than it uses its feet for prehension, trusting much to its prehensile tail, shows its corrugated epidermis and papillary ridges developed in about equal proportions. These five mammals thus show that the stimuli of pressure and friction and the response to them are being complicated by the addition of the more delicate tactile organs known as papillary ridges, and these, perhaps, in a secondary way are becoming useful in preventing friction. But I must not omit to point out that, _quâ_ prevention of slipping, the few sparse papillary ridges of the _hedgehog_, _squirrel_, _kinkajou_ and _flying-phalanger_, especially those on the extreme tips of the digits, could have no effect in this prevention and no survival value. It is otherwise when they are developed in large areas as in the succeeding groups. Primates. All the thirty species of Primates possessed papillary ridges to such an extent that only small areas of the palmar and plantar skin of the lemurs showed any other than these remarkable characters. It is so much a property of the Primate hand and foot to possess these that it might be almost made a matter of ordinal rank belonging to the Primates, were it not that a few stray lower mammals also possess it.