can thus see what are the deficiencies in his collection, and from what countries he most needs additional species; and all this information I wished to give him, as I had often felt the want of it myself. This part of the work I termed "geographical zoology," and to this I gave special attention, and have given for every family of mammals, birds, and reptiles a diagram, which in a single line exhibits its distribution in each of the four subregions of the six regions. To give the reader some idea of this compact method of summarizing information, I will give here its application to one family of mammalia:

FAMILY 50-CERVIDA (8 genera 52 species).

Here the distribution of the true deer over the earth is shown at a glance when once the limits of the regions and subregions are learnt, as marked on the general and special maps by which the book is illustrated. The work was published in 1876, in two thick volumes, and it had occupied a good deal of my time during the four years I lived at Grays. As this book, being very costly and technical, is less known to English readers than any of my other works, I will here give the titles of the chapters, which will sufficiently indicate the range of subjects treated in its eleven hundred pages:

PART I.-THE PRINCIPLES AND GENERAL PHENOMENA OF
DISTRIBUTION.

Chap. I. Introductory.

II. The means of Dispersal and the Migrations of Animals.
III. Distribution as affected by the Conditions and Changes

of the Earth's Surface.

IV. The Zoological Regions.

V. Classification as affecting the Study of Geographical Distribution.

PART II.-ON THE DISTRIBUTION OF EXTINCT ANIMALS.

Chap. VI. The Extinct Mammalia of the Old World.

VII. Extinct Mammalia of the New World.

VIII. Various Extinct Animals; and on the Antiquity of the
Genera of Insects and Land Shells.

PART III.-ZOOLOGICAL GEOGRAPHY: A REVIEW OF THE CHIEF FORMS OF LIFE IN THE SEVERAL REGIONS AND SUBREGIONS, WITH THE INDICATIONS THEY AFFORD OF GEOGRAPHICAL CHANGES.

Chap. IX. The Order of Succession of the Regions-Cosmopolitan Groups of Animals-Tables of Distribution.

XV. The Nearctic Region.

XVI. Summary of the Past Changes and General Relations of the Several Regions.

PART IV.-GEOGRAPHICAL ZOOLOGY: A SYSTEMATIC SKETCH OF THE CHIEF FAMILIES OF LAND ANIMALS IN THEIR GEOGRAPHICAL RELATIONS.

Chap. XVII. Distribution of the Families and Genera of Mam

XVIII.
XIX.

malia.

Distribution of the Families and Genera of Birds. Distribution of the Families and Genera of Reptiles and Amphibia.

XX. Distribution of the Families of Fishes, with the Range of such Genera as inhabit Fresh-water. XXI. Distribution of some of the more important Families and Genera of Insects.

XXII.
XXIII.

Outline of the Geographical Distribution of Mollusca. Summary of the Distribution and Lines of Migration of the Several Classes of Animals.

I devoted a large amount of labour to making a fairly complete index, which comprises more than six thousand entries.

No one is more aware than myself of the defects of the

work, a considerable portion of which are due to the fact that it was written a quarter of a century too soon-at a time when both zoological and palæontological discovery were advancing with great rapidity, while new and improved classifications of some of the great classes and orders were in constant progress. But though many of the details given in these volumes would now require alterations, there is no reason to believe that the great features of the work and general principles established by it will require any important modification. Its most severe critics are our American cousins, who, possessing a "region" of their own, have been able to explore it very rapidly; while from several references made to it, I think it is appreciated on the European continent more than it is in our own country.

While this work was in progress I wrote a considerable number of reviews and articles, published my book on "Miracles and Modern Spiritualism," and wrote the article "Acclimatization" for the "Encyclopædia Britannica."

In 1876 I sold the house at Grays and removed to Dorking, where we lived two years. But finding the climate relaxing, we moved next to Croydon, chiefly in order to send our children first to a kindergarten, and then to a high school, and remained there till May, 1881.

During this period, besides my usual reviews and articles, I prepared my address as president of the Biological Section. of the British Association at Glasgow, wrote the article on “Distribution—Zoology" for the "Encyclopædia Britannica," and prepared a volume on "Tropical Nature," which was published in 1878. In this work I gave a general sketch of the climate, vegetation, and animal life of the equatorial zone of the tropics from my own observations in both hemispheres. The chief novelty was, I think, in the chapter on "climate,” in which I endeavoured to show the exact causes which produced the great difference between the uniform climate of the equatorial zone, and, say, June and July in England, although at that time we receive actually more of the light and heat of the sun than does Java in June or Trinidad in December. Yet these places have then a mean temperature