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NE of the most valuable of the many important contributions of the National Geographic Society to popular education is Edward W. Nelson's account of the mammals of North America,1 with colored illustrations by Louis Agassiz Fuertes, track illustrations by Ernest Thompson Seton, and half-tone reproductions of photographs of especial interest and pertinence, published, as stated by the editor of the magazine, at a cost of $100,000. The account was originally issued in two parts, "The Larger North American Mammals," in November, 1916, and the "Smaller Mammals of North America," in May, 1918. The two parts are now issued together in book form, greatly facilitating their use as a convenient work of reference, useful alike to the naturalist and the general reader.

Excellent books on North American birds, many of them well illustrated, have long been available, and also a number of magazines exclusively devoted to these easily observed dwellers in our midst, graceful and attractive in form as well as vivacious and songful, their nest building and manner of life open to all observers. It is easy for anyone with the slightest interest in these wonderful creations to know intimately their life habits and to have a fair knowledge of perhaps a hundred species that frequent their home surroundings of field and woodland. On the other On the other hand, it is safe to say that the wild mammals equally well known to them can be counted on the fingers of a single hand, and of only two or three of which will they have more than slight knowledge of their manner of life.

1 Wild Animals of North America: Intimate Studies of Big and Little Creatures of the Mammal Kingdom. By Edward W. Nelson. Published by the National Geographic Society, Washington, D. C., 1918.

Mammals have, as a rule, no vocal powers to attract attention; they are, for the most part, secretive and nocturnal in habits. Of the hundreds of field mice and shrews and moles that inhabit the fields and meadows through which we daily walk only a rare accident may bring even one of them to our ken. Only the hunter and the trapper know the haunts of the fur bearers and the game animals. Only the professional field collector, with his resources of skill and of especially devised traps, has the opportunity and the required knowledge to unveil the mysteries of our smaller mammal life. There is no "color key" or other popular device to aid the amateur in finding out the names and relationships of the forms he may chance to obtain. The recognition of their distinctive features requires more or less technical training on the part of the observer before he can determine the specimen he may chance to have acquired.

The requisites of an author who could successfully prepare a volume like the present one are numerous and varied. Fortunately, Mr. Nelson, chief of the United States Biological Survey, is the possessor of them all in a high degree. Inspired with a love of the wild and, above all, with the spirit of research and discovery, his natural history explorations have taken him throughout the continent from the Arctic tundras of Alaska to the jungles of tropical Mexico, and have made him familiar alike with the life of the desert and the forest. While an ardent ornithologist, he is equally an ardent mammalogist and a broadly trained naturalist able to impart his experiences and observations with sympathy and directness. He has lived with the animals

of which he writes and has studied them in their homes; on the technical side he is a monographer of many of the groups of which he so tersely and clearly sets forth the life histories.

The forms (species and local races) of mammals now recorded from continental North America number nearly 2500, yet they are reducible, so far as their distinctive traits are concerned, to a few hundred types. As North America, in the sense of the present work, is mainly the continent north of the tropics, Nelson's biographies of about 120 groups comprise all of the types of this large area which are of primary interest, from the large game and fur-bearing animals to the bats, shrews, mice, and squirrels. Thus, the hares and rabbits, numbering approximately one hundred local forms that are considered worth distinguishing under the "higher criticism" of modern days, are treated as constituting six groups, each illustrated in color, and the distinctive external characteristics and habits of the constituents of each are clearly and satisfactorily presented. Never before has the general reader had placed before him in a connected and well balanced summary so much essential information about North American hares and rabbits. And the same is true of all the other biographies.

Mr. Nelson, in his introductory pages, contrasts the early days of the settlement of North America with present conditions in respect to the larger mammalian life of the continent-the abundance in the seventeenth and eighteenth century times and the pitiful remnants that now remain-and makes a strong appeal for the conservation of wild life. In the introduction to the second part, the "Smaller Mammals of North America," a dozen pages are given to the generalities of the subject, which are condensed under such suggestive subheadings as "Animals that learned to dig in,'" "A departure for every need," "Strange adaptations to

meet conditions of environment and competition," "Geography and color," "Gnawers most numerous of mammals," "Good housekeeping in rodent land," "The ebb and flow of antagonistic species," "Countless beasts that roam the night," "Animals that put themselves in cold storage," "Defensive and offensive animal alliances," etc. Under these captions are presented a wide range of general statements and philosophic deductions, as the evident close relationship of certain northern forms to Old World types, and the presence on our southern border of a similar affiliation. with tropical American types, while others still are distinctly of North American origin with no close relationship to groups found elsewhere.

The special adaptations of species to their particular environments, and to very diverse conditions of life, as arboreal, subterranean, aquatic and aërial, and the modifying effect of climatic conditions, resulting in the development of geographic races in species which have a wide range, are also among the topics presented. The ability of desert inhabiting species to live without drinking, "through chemical action of their digestive tracts, whereby some of the starchy parts of their food. are changed into water," is also noted; also the storing of food for winter use by some species, while others pass the winter in a torpid condition and thus do not require food. Molting, or the seasonal change of the coat, is also the subject of comment, and likewise the concurrent change of color from brown to white in autumn and the reverse in spring in many northern animals as a protective provision against enemies. In this connection a misapprehension of former days in respect to how the change in color is brought about is, let us hope, finally given its quietus by this statement of the now known facts of the case: "It was formerly considered that the change of mammals from the brown of summer to the white winter

coat in the fall, and from the white to the brown in spring, was due to a change in the color of the hairs, but it is now known that it is entirely due to molt. The time of these changes depends on the season, and this varies several weeks, according to whether the fall or spring is late."

Mr. Seton's illustrations and descriptions of the footprints of a large number of different kinds of mammals, when walking and when running, add a novel and interesting feature from a field that he has made practically his own. The subjects range from bears, coyotes, and other carnivores to deer, moose, and caribou among the larger mammals, and from jack rabbits and squirrels to field mice and shrews. They will vividly recall to many readers the imprints seen by them in newly fallen snow during many a winter walk

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in the country. In these sketches, entitled "Footprints of Nature's Wild Folk," Mr. Seton tells us he "usually gives the track of a normal adult animal in about one inch of snow, that being ideal for tracking. Some of the smaller kinds are shown in fine dust. The trail goes up or across the page at the ordinary gait of the animal. . . . While there are endless variants in each kind, I aim to give the reader at least one typical set of each." There are nearly sixty of these sketches, which represent the leading types of mammals. over a wide range of country.

Mr. Fuertes' colored illustrations are of course of the highest excellence, and give the reader a vivid conception of the varied forms of mammal life in North America. Our foremost bird draftsman may now be awarded equal honor in another field.