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fashion, and then put spoonful after spoonful of marmalade in, till the cup was full. “That is very nice,” he said ; and he had another cup of the same mixture. I love delicacies myself, and these little eccentricities interested me; but I draw the line at marmalade and tea.
At this time I was somewhat doubtful in what particular direction to work, as I found that I could not now feel sufficient interest in any branch of systematic zoology to devote myself to the minute study required for the classification and description of any important portion of my collections. There were many other men who could do that better than I could, while my special tastes led me to some work which involved a good deal of reasoning and generalization. It was, I think, my two friends, Professor A. Newton and Dr. Sclater, who urged me to undertake a general review of the geographical distribution of animals, and after a little discussion of the subject I came to the conclusion that I might perhaps be able to do it; although, if I had been aware of the difficulties of the task, I should probably not have undertaken it.
As this was the largest and perhaps the most important scientific work I have done, I may perhaps be allowed here to say a few words as to its design and execution. I had already, in several of my papers and articles, explained my general views of the purport and scope of geographical distribution as a distinct branch of biological science. I had accepted and supported Dr. P. L. Sclater's division of the earth's surface into six great zoological regions, founded upon a detailed examination of the distribution of birds, but equally applicable to mammalia, reptiles, and several other great divisions, and best serving to illustrate and explain the diversities and apparent contradictions in the distribution of all land animals; and I may now add that the additional facts accumulated, and the various divisions suggested during the thirty years that have since elapsed, have not in the least altered my opinions on this matter.
In whatever work I have done I have always aimed at
systematic arrangement and uniformity of treatment throughout. But here the immense extent of the subject, the overwhelming mass of detail, and above all the excessive diversities in the amount of knowledge of the different classes of animals, rendered it quite impossible to treat all alike. My preliminary studies had already satisfied me that it was quite useless to attempt to found any conclusions on those groups which were comparatively little known, either as regards the proportion of species collected and described, or as regards their systematic classification. It was also clear that as the present distribution of animals is necessarily due to their past distribution, the greatest importance must be given to those groups whose fossil remains in the more recent strata are the most abundant and the best known. These considerations led me to limit my work in its detailed systematic groundwork, and study of the principles and laws of distribution, to the mammalia and birds, and to apply the principles thus arrived at to an explanation of the distribution of other groups, such as reptiles, fresh-water fishes, land and freshwater shells, and the best-known insect-orders.
There remained another fundamental point to consider. Geographical distribution in its practical applications and interest, both to students and the general reader, consists of two distinct divisions, or rather, perhaps, may be looked at from two points of view. In the first of these we divide the earth into regions and subregions, study the causes which have led to the differences in their animal productions, give a general account of these, with the amount of resemblance to and difference from other regions; and we may also give lists of the families and genera inhabiting each, with indications as to which are peculiar and which are also found in adjacent regions. This aspect of the study I term zoological geography, and it is that which would be of most interest to the resident or travelling naturalist, as it would give him, in the most direct and compact form, an indication of the numbers and kinds of animals he might expect to meet with.
But a large number of students now limit themselves to a study of one of the classes, or even orders, of the higher
animals from all parts of the world, and it is of special interest to him to be able to see at a glance how each family and genus is distributed, with the number of known species. He 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-CERVIDÆ (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 1.—THE PRINCIPLES AND GENERAL PHENOMENA OF
II. The means of Dispersal and the Migrations of Animals.
PART II.-ON THE DISTRIBUTION OF EXTINCT ANIMALS.
VII. Extinct Mammalia of the New World.
Genera of Insects and Land Shells.
PART III.-ZOOLOGICAL GEOGRAPHY: A REVIEW OF THE CHIEF FORMS OF LIFE IN THE SEVERAL REGIONS AND SUBREGIONS,
INDICATIONS THEY AFFORD OF GEOGRAPHICAL
Groups of Animals—Tables of Distribution.
XV. The Nearctic Region.
the Several Regions.
PART IV.-GEOGRAPHICAL ZOOLOGY : A SYSTEMATIC SKETCH OF THE
CHIEF FAMILIES OF LAND ANIMALS IN THEIR GEOGRAPHICAL
Chap. XVII. Distribution of the Families and Genera of Mammalia.
XVIII. Distribution of the Families and Genera of Birds.
such Genera as inhabit Fresh Water,
Genera of Insects.
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 VOL. II.
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 alteration, 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 very much higher than ours. It contained also a chapter on