NATURE 



137 



THURSDAY, AUGUST 3, 1911. 



ZOOGEOGRAPHY. 

 Bartholomew's Physical Alias, vol. v.. Atlas of Zoo- 

 graphy: a Series of Maps Illustrating the Dis- 

 tribution of ovei Seven Hundred Families, Genera, 

 and Species of Existing Animals. Prepared by Dr. 

 J. G. Bartholomew, W. Eagle Clarke, and P. H. 

 Grimshaw. Pp. viii + 67 + 36 plates + xi. (Edin- 

 burgh : J. Bartholomew and Co., 1911.) Price 

 2I. J2S. 6d. net. 



THE fifth volume of " Bartholomew's Physical 

 Atlas " is devoted to " Zoogeography " — that is, 

 as the word clearlv indicates, the science of the dis- 

 tribution of animal-life over the world's surface. 

 Little was known and still less was understood about 

 this branch of zoology in former years. But when 

 the "Origin of Species" began to be discussed it was 

 quicklv perceived how closely the localities of animals 

 and plants are connected with their affinities, and 

 how important "zoogeography" is to the student of 

 animal and vegetable life. Linnaeus and his imme- 

 diate followers did not understand this. They thought 

 that such terms as " East Indies " or " Brazil " were 

 quite sufficient indications of the locality of an animal. 

 But, as the science of zoology advanced, authors be- 

 came gradually more particular as to their localities, 

 and nowadays unless the place of origin is exactly 

 known a specimen loses at least half its value. In 

 early days the faunal character of each geographical 

 area was supposed to depend entirely on its climatic 

 and physical peculiarities. This idea, however, has 

 been abundantly proved to be incorrect. In many 

 case> tracts of the world's surface exactly similar in 

 climate and in other physical conditions can be shown 

 to be entirely different as regards their animal life. 

 It was not until the theory that the descent of 

 animals is accompanied by modifications of their 

 structure became appreciated that any correct views 

 wen- put forward on the laws of their geographical 

 distribution. The authors of the present work de- 

 scribe the commencement of this new period as 

 s : — 



"The first attempt to map out a set of zoogeograph- 

 ical regions, based upon the actual distribution of 

 spi 1 ii -, and apart altogether from purely geographical 

 considerations, was made by Dr. P. L. Sclater. This 

 eminent zoologist, who is, fortunately, still living, 

 a paper before the Linnean Society of London, in 

 June. 1857, entitled ' On the General Geographical 

 Distribution of the Members of the Class Aves. ' 

 Taking as his basis the Passerine, or ' Perching ' 

 Birds, he proposed the division of the earth into six 

 regions, which he defined geographicallv, and 

 whose area in square miles he roughly estimated. At 

 the same time, he furnished a tabulated statement of 

 the number of species found in each region, and 

 gavi an indication ol the peculiar and characteristic 

 genera. As this paper was an epoch-making one, 

 and as its divisions correspond very closely with the 

 main regions adopted in most of the schemes since 

 proposed, it is perhaps desirable to quote the main 

 features before proceeding further." 



XO. 2 1-g, VOL. 8/] 



The authors then proceed to enumerate the six 

 great "regions" into which Dr. Sclater had proposed 

 to divide the earth's surface for zoological purposes, 

 adding in each case a short description of their boun- 

 daries and estimated areas, also a rough calculation 

 of the number of species of birds then known to be 

 found in each of them. These six regions were as 

 follows :— (1) The Palaearctic region (embracing 

 Europe and North Asia, and the northern part of 

 North Africa) ; (2) the Ethiopian region (Africa, except 

 the portion north of the Sahara) ; (3) the Indian region 

 (southern Asia and the adjacent islands); (4) the Aus- 

 tralian region (Australia and the Pacific Islands); (5) 

 the Nearctic region (North America); and (6) the 

 Neotropical region (South and Central America). 



The publication of Dr. Sclater's article induced 

 many other zoologists to state their views on the 

 subject. Giinther, Blanford, Huxley, Heilprin, and 

 Blvth were among the number. Many of them agreed 

 more or less with Dr. Sclater's proposals, but offered 

 criticisms on particular points, and suggested emenda- 

 tions of his nomenclature. But in 1876 appeared Dr. 

 Wallace's classical and important work, "On the 

 Geographical Distribution of Animals," which com- 

 bined all that had been previously known on the 

 subject with the knowledge acquired by the travels 

 and experiences of this great naturalist. In this work 

 Dr. Wallace absolutely adopted Dr. Sclater's division 

 of the world into six great regions and his nomen- 

 clature, only suggesting that the name of the 

 " Indian " region should be changed to the "Oriental " 

 region, an improvement which subsequent authors 

 have been generally willing to agree to. 



Dr. Wallace, after fully considering the question, 

 states decisively his reasons for adopting the six 

 zoological regions proposed by Dr. Sclater as fol- 

 lows : — 



"So that we do not violate any clear affinities or 

 produce any glaring irregularities, it is a positive, 

 and bv no means an unimportant advantage to have 

 our regions approximated equal in size, and with 

 easily defined, and therefore easily remembered, 

 boundaries. All elaborate definitions of interpenetrat- 

 ing frontiers, as well as regions extending over three- 

 fourths of the land-surface of the globe, and including 

 places which are the antipodes of each other, would 

 be most inconvenient, even if there were not such 

 great differences of opinion about them. There can be 

 little doubt, for example, that the most radical zoo- 

 logical division of the earth is made by separating the 

 Australian region from the rest; but although it is 

 something useful and definite to know that a group 

 of animals is peculiar to Australia, it is exceedingly 

 vague and unsatisfactorv to say of any other group 

 merely that it is extra-Australian. Neither can it be 

 said that, from any point of view, these two divisions 

 are of equal importance. The next great natural divi- 

 sion that can be made is the separation of the ' Neo- 

 tropical ' region of Dr. Sclater from the rest of the 

 world. We "should thus have three primary divisions, 

 which Prof. Huxlev seems inclined to consider as of 

 tolerablv equal zoological importance. But a considera- 

 tion of" all the facts, zoological and palaeontological, 

 indicates that the great northern division (Arctoga?a) is 

 fully as much more important than either Australia or 

 South America, as its four component parts are less 



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