The she-bear is taught by a wonderful instinct to shelter her young under the snow. Towards the month of December she retreats to the side of a rock, where, by dint of scraping and allowing the snow to fall upon her, she forms a cell in which to reside during the winter. There is no fear that she should be stifled for want of air, for the warmth of her breath always keeps a small passage open, and the snow, instead of forming a thick uniform sheet, is broken by a little hole, round which is collected a mass of glittering hoar-frost, caused by the congelation of the breath. Within this strange nursery she produces her young, and remains with them beneath the snow until the month of March, when she emerges into the open air with her baby bears. As the time passes on, the breath of the family, together with the warmth exhaled from their bodies, serves to enlarge the cell, so that with their increasing dimensions the accommodation is increased to suit them. As the only use of the snow-burrow is to shelter the young, the male bears do not hibernate like the females, but roam freely about during the winter months. Before retiring under the snow, the bear eats enormously, and, driven by an unfailing instinct, resorts to the most nutritious diet, so that she becomes prodigiously fat, thus laying in an internal store of alimentary matter which enables her not only to support her own life, but to suckle her young during her long seclusion, without taking a morsel of food. By an admirable provision of nature, the young are of wonderfully small dimensions when compared with the parent; and as their growth, as long as they remain confined in their crystal nursery, is remarkably slow, they consequently need but little food and space. [Illustration: 37. HOME OF THE POLAR BEAR.]