NA TURE 



165 



THURSDAY, JUNE 22, 1876 



WALLACE'S GEOGRAPHICAL DISTRIBUTION 

 OF ANIMALS 



The Geographical Dist7-ibtition of Animals, with a Study 

 of the Living and Exilnct Faujias, as Elucidatiiij( the 

 Past Changes of the Earth^s Surface. By Alfred 

 Russel Wallace. Two ^'ols. 8vo. (London : Mac- 

 millan and Co., 1876.) 



THE question of the number and boundaries of the 

 primary zoological regions of the Globe has recently 

 been discussed by Prof. Newton in his article on "Birds," 

 in the new edition of the " Encyclopcedia Britannica." 

 After remarks on the failure of previous writers to solve 

 this problem in a satisfactory manner, Prof. Newton 

 comes to the conclusion that the outlines of distribution 

 laid down in 1857 by Mr. Sclater, although founded only 

 upon the study of the erratic class of birds, have " not 

 merely in the main, but to a very great extent in detail, 

 met with the approval of nearly all those zoologists who 

 have since studied the subject in its bearing upon the 

 particular classes in the knowledge of which they them- 

 selves stand pre-eminent." In point of fact, Mr. Wallace 

 himself was one of the first naturalists to accept Mr. 

 Sclater's views on this subject. Writing from the remote 

 island of Batchian, in the Indian Archipelago, in March 

 1859, after perusing Mr. Sclater's well-known memoir on 

 the Geographical Distribution of Birds,^ Mr. Wallace says, 

 in a letter to Mr. Sclater published in the first volume of 

 the Ibis^ " With your division of the earth into six grand 

 zoological provinces I perfectly agree, and I believe they 

 will be confirmed by every other department of zoology 

 as well as by botany." In the two excellent volumes now 

 before us, in which are embodied the results of several 

 years continuous labour upon this and kindred branches 

 of the same subject, it will be seen that Mr. Wallace has 

 not altered his opinion. The six great primary zoological 

 regions of the globe proposed by Mr. Sclater in 1857 are 

 fully adopted, and form the basis of Mr. Wallace's whole 

 treatment of the subject. But one slight change even in 

 their nomenclature is made — that of substituting " Oriental " 

 as the name of the Region embracing South Asia and the 

 adjacent islands for Mr. Sclater's term " Indian." In 

 fact, after discussing the general principles and pheno- 

 mena of distribution and what little we as yet know con- 

 cerning the distribution of extinct animals, the main 

 portion of Mr. Wallace's volumes is occupied by an 

 elaborate sermon on Mr. Sclater's text, and on its appli- 

 cation to other classes of animals. The various pheno- 

 mena of life exhibited in the Palaearetic, Ethiopian, 

 Oriental, Australian, Neotropical, and Nearctic regions 

 are treated of in succession, and their similarities and 

 their differences are discussed. To this is added a sketch 

 of the geographical distribution of the principal families 

 of terrestrial animals arranged systematically, which 

 forms the fourth part of this important work. Of this 

 last portion, which is, in fact, a book of reference contain- 

 ing an account of the distribution of all the families, and 



* See " Journal of the Proceedings of the Linnean Society," Zoology, ii. 

 p. 130. 



" Letter from Mr. Wallace concerning the Geographical Distribution of 

 Birds. {Ibis, 1859, pp. 449.) 



Vol. XIV. — No. 347 



of most of the genera of the higher animals arranged in 

 systematic order, we propose to speak in a subsequent 

 article. For the present we will confine our attention to 

 the first three parts of Mr. Wallace's work. 



The introductory chapter, with which the first volume 

 of the " Geographical Distribution of Animals " is com- 

 menced, although it states the object of the work plainly 

 enough to the mind of the scientific reader, seems a little 

 too brief and concise to explain the nature of the 

 problem under discussion to the general public. It must 

 be borne in mind that the very idea of the existence of 

 any regular laws of distribution is a novelty to most 

 people— §vw, we regret tQ say, to many who call them- 

 selves naturalists. It is to be regretted, therefore, we 

 think, that Mr. Wallace has not devoted a few more 

 pages to the general explanation of the subject of which 

 he treats, to the pointing out of the many subordinate 

 problems which it involves, and in particular to the further 

 explanation and definition qf such technical terms as 

 " habitat," " stMlppa,'' ♦* range," and " representative 

 species," which confront us in some of the very first 

 pages of his work. 



In his second chapter Mr. Wallace discusses the 

 means by which animals are dispersed, and devotes 

 a good deal of space to the question of migration. 

 Now, migration is, m doubt a very important pheno- 

 menon, but whether it has much to do with the general 

 theory of distribution appears to be rather doubtful. It 

 occurs only in one or two groups of animals ; and, as 

 Mr. Wallace himself observes, " we must, except in 

 special eases, consider the true range of a species to com- 

 prise all the area which it occupies regularly for any part 

 of the year." Migration, therefore, primarily affects the 

 distribution of a species within its own specific area, and 

 only has to do with the general question of distribution 

 so far as it may increase the tendency of a species to 

 vary its range. With Mr. Wallace's views on the subject 

 of dispersal generally wc cordially agree. There can 

 be no question that, in the ** glacial epoch " and in the 

 more recent geological changes which have taken place 

 on the earth's surface, the key of the present complicated 

 phenomena of distribution should be sought, although 

 many of them have had a much earlier origin. "Almost 

 every mile of land-surface has been again and again 

 depressed beneath the ocean ; most of the great mountain 

 chains have either originated or greatly increased in height 

 during the Tertiary period j marvellous alterations of 

 climate and vegetation have taken place over half the 

 land-surface of the earth ; and all these vast changes 

 have influenced a globe so cut up by seas and oceans, by 

 deserts and snow-clad mountains, that in many of its 

 more isolated land-masses, ancient forms of life have 

 been preserved, which, in the more extensive and more 

 varied continents have long given way to higher types." 



Mr. Wallace now proceeds to enter upon the grand 

 question of Zoological Regions, entirely ignored, as he 

 truly says, by the older school of naturalists. To them, 

 provided they got the object, it little mattered whence it 

 came. " The Brazils," the " East Indies," or the " South- 

 sea Islands," was considered ample information as to the 

 locality of any specimen, even if it were thought neces- 

 sary to give such information at all. How could such 

 men appreciate the idea of Zoological Regions ? They 



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