Page:Popular Science Monthly Volume 34.djvu/207

Rh types still hold out in extreme recesses or under special climatic and geographical conditions; and thus the llama and alpaca have been preserved to our time intact in the narrow belt of temperate slope between the snow-clad Andes and the Pacific shore.

I have said that the cameloids are a very ancient type of ruminants indeed: their skeleton abundantly proves this fact; but I will not dwell at length upon such dry points of anatomical detail, because I fancy I have noticed on various occasions that the general public does not wildly interest itself in questions of carpal and metatarsal bones. It is not frantically enthusiastic about distinctions of odd-toed or even-toed ungulates. What most of us really want to know, and what the comparative anatomists as a body still studiously neglect to tell us in plain language, is how each animal came to obtain, not its bones which we don't see, but its distinctive external shape and characteristics—its horns, its tusks, its hump, or its antlers. We would rather learn a few simple facts about the evolution of the elephant's trunk or the peacock's tail than a whole volume of learned memoirs on the cervical vertebræ and the carinate sternum. Those things are doubtless very convincing in their own way, but they are not of a sort to rouse our profound personal attention. There are, however, two other visible points about the camel-kind which clearly mark their true position as very early ruminants indeed, and which can yet be readily apprehended by the ordinary surface-loving, non-anatomical intelligence. One is, that the camels as a group antedate the development of horns or antlers; the other is that they still possess in full, like other animals, those canine and incisor teeth which are partly obsolete, partly altered in shape, in all the higher and later ruminants. Each of these peculiarities has a meaning of its own, and points back to certain interesting episodes in the development of the great ruminant order.

The vast mass of ruminants generally at the present day possess some form or other of horns or their equivalents. In the giraffe, which in a few points (mostly delusive) approaches the camels, the horns are merely blunt protuberances of bone, persistent through life, and covered with a continuous hairy skin. They show us the lowest surviving stage in the evolution of frontal weapons. In the deer tribe, they appear at first under much the same form, as little knobs or bosses of bone on the forehead, underlying a fold of skin technically known as the velvet; but when the horns are fully grown, the velvet is rubbed off, and the bone alone shows its naked material as the branching antlers with which we are all so familiar in the Scotch red deer. Horns of this type are shed annually, and reproduced in more and more complex forms (representing successive ancestral stages) with each renewal. Finally, in the great central group of the