In some ways these animals are not unlike antelopes. But one great difference between the two is this. In the antelopes the horns are hollow, growing upon bony cores which spring from the skull, and remain all through the life of the animal. But in the deer they are solid, and are thrown off every year, fresh ones growing in their places in the course of four or five months. Then the material of which they are made is altogether different, for whereas the horns of the antelopes really consist of highly compressed hair, those of the deer are composed of lime, and are very much more like bone. On account of these differences horns of deer are better called antlers. The way in which these antlers grow is very curious. For some little time after they are shed the animal is extremely timid, for he knows perfectly well that he has lost his natural weapons. So he hides away in the thickest parts of the forest, where none of his enemies are likely to find him. After a while, two little knobs make their appearance on the head, just where the horns used to be. These knobs are covered with a close furry skin, which is known as the velvet, and if you were to take hold of them you would find that they were quite hot to the touch. That is because the blood is coursing rapidly through them, and leaving particles of lime behind it as it goes. Day by day they increase in size, throwing out branches as they do so, until they are rather larger than the pair which were cast off. Then the blood-vessels close up, and the velvet becomes dry and begins to fall off, sometimes hanging down in long strips, which are at last rubbed off against the trees and bushes. REINDEER AND CARIBOU A great many kinds of deer are found in different parts of the world, perhaps the most famous of all being the reindeer. This is the only deer in which the does possess horns as well as the stags. It is found in the northern parts of Europe and Asia and also of North America, where it is called the caribou and generally lives in large herds. During the winter and spring these herds remain in the forests. But in summer they are so annoyed by flies that they make their way to the hills, ascending to such a height that their insect enemies cannot follow them, and there they remain until the autumn. A number of herds usually join together when they are migrating in this way, and the appearance of thousands upon thousands of the animals traveling slowly along, each with its antlers uplifted, has been compared to that of a moving forest of leafless trees. In Siberia, Lapland, and Norway, large herds of reindeer are kept as we keep cattle, and are used as beasts both of draught and burden. A single reindeer can carry a weight of about 130 pounds upon its back, or draw a load of 190 pounds upon a sledge, and it so enduring that it will travel at the rate of from eight to ten miles an hour for twelve hours together.