Under favorable conditions they steadily increase until they become enormously plentiful over great areas. After this swarming abundance continues for several seasons it reaches a maximum, and then, as in the case of many other mammals when similarly overabundant, a mysterious malady suddenly attacks and sweeps them off, until within a year or two they become rare over the entire area. The people of the fur country believe these changes in numbers run in cycles of about seven years each. As the hares increase in numbers some of the birds and mammals which prey upon them increase proportionately. This is specially marked with the big northern lynxes. The skins of varying hares are gathered and sent to the London fur market with other furs, including those of lynxes. In the records of sales of the Hudson’s Bay Company there are direct increases of the numbers of Canada lynx skins sold corresponding with the increases in the sales of varying hare skins. As the number of hare skins abruptly decreases following the outbreak of epidemics among them, there are correspondingly abrupt decreases in the numbers of lynx skins sold. This correlation is shown in the records extending back many years and illustrates the interdependence in nature between the various forms of animal life. The far-reaching tragic effect of the sudden disappearance of the snowshoe rabbits is not confined to the wild habitants of the forest, as it has not infrequently brought starvation and death into many lonely Indian lodges in the great northern wilderness. =THE ARCTIC HARE= (=Lepus arcticus= and its relatives) (_For illustration, see page 510_) Many parts of the northernmost circumpolar lands are occupied by large hares, which attain a weight of more than ten pounds. They are about the size of large jack rabbits, but are more heavily proportioned, with much shorter ears and shorter, stronger legs. There are several species and geographic races of these animals, all of which are snowy white in winter except for a small black tip on each ear. In summer the southern arctic hares change to a nearly uniform dull iron gray or grayish brown. The northernmost animals of Ellesmere Land and north Greenland, where the summer is brief and severe arctic conditions prevail, retain their white coat throughout the year. In keeping with the cold climate of their territory, the furry coat of the arctic hares is long and thick, especially in winter, when the ears, legs, and even the soles of +he feet, as well as the body, are heavily furred. The coats of the hares of north Greenland and adjacent region are so heavy and fleecelike that during the spring molt they come off in felted patches as the new coat is assumed, giving the hares a curiously ragged appearance.