cular arrangement of the individual hairs among mammals; they are not by any manner of means scattered without order, but show a definite and regular arrangement, which varies with the animal. For instance, in an American Monkey (Midas), the hairs arise in threes—three hairs of equal size springing from the epidermis close together; in the Paca (Coelogenys) there are in each group three stout hairs alternating with three slender hairs. In some forms a number of hairs spring from a common point: in the Jerboa (Dipus) twelve or thirteen arise from a single hole; in Ursus arctos there is the same general plan, but there is one stout hair and four or five slender ones. There are numerous other complications and modifications, but the facts, although interesting, do not appear to throw any light upon the mutual affinities of the animals. Allied forms may have a very different arrangement, while in forms which have no near relationship the plan may be very similar, as is shown by the examples cited from Dr. Meijerle's paper. The groups of hairs, moreover, have themselves a definite placing, which the same anatomist has compared with the disposition of the bundles of hairs behind and between the scales of the Armadillo, and which has led him to the view that the ancestors of mammals were scaly creatures—a view also supported by Professor Max Weber,[1]and not in itself unreasonable when we consider the numerous points of affinity between the primitive Mammalia and certain extinct forms of reptiles.[2]
The hairs are greatly modified in form in different mammals and in different parts of their bodies. It is very commonly the case that a soft under-fur can be distinguished from the longer and coarser hairs, which to some extent hide the latter. Thus the "sealskin" of commerce is the under-fur of the Otaria ursina of the North. The coarser hairs may be further differentiated into bristles; these again into spines, such as those of the Hedgehog and of the Porcupine. Again, the flattening and agglutination of hairs seems to be responsible for the scales of the Manis
- ↑ "Bemerkungen über den Ursprung der Haare," Anat. Anz. 1893, p. 413.
- ↑ See for this matter, p. 90. Dr. Bonavia has recently advanced (Studies in Evolution, London, 1895) the somewhat fantastic view that the pigment-patches of Carnivorous and other mammals are a reminiscence of an earlier scaly condition. There is no direct evidence that the primitive mammals were scaly, nor are the Monotremata or Marsupials furnished with any more traces of such a condition than are other mammals; and they are the most lowly organised of existing Mammalia.
