NATURE 



357 



THURSDAY, FEBRUARY 17, 1S81 



ISLAND LIFE 

 Island Life; or, The Phenomena and Causes of Insular 

 Faunas and Floras, including a Revision and At- 

 tempted Solution of the Problem of Geological Climates. 

 By Alfred Russel Wallace. (London : Macmillan and 

 Co., 1880.) 



I. 



MR. WALLACE is to be congratulated on his success 

 in that most difficult part of book-writing — the 

 choice of a good descriptive, yet short and euphonious, 

 title. " Island Life ! " What do not the words suggest ! 

 How many old associations do they not recall ! A vacant 

 and unsuspicious reader may indeed be lured by them to 

 open what he may expect will prove a good novel, perhaps 

 a story of the "Robinson-Crusoe" type. His hopes will 

 be quenched by the first chapter ; but if he possesses 

 any capacity for an interest in the flowers, insects, birds, 

 and beasts of his home, it will almost certainly be quick- 

 ened by a perusal of that chapter. Like a skilful com- 

 poser Mr. Wallace strikes at once with a firm touch the 

 key-note of his volume. In a few pages he puts before 

 us the problem he seeks to solve, and does this in so 

 graphic and masterly a way that most readers will not 

 only comprehend what he aims at, but will be persuaded 

 into the belief that as they are familiar with some parts 

 of the subject they have a personal interest in seeing 

 what the author can make of it. 



Hardly any problem in modern science is at once so 

 complex and so fascinating as the geographical distribu- 

 tion of plants and animals. Strange to say, this com- 

 plexity and fascination have steadily increased with the 

 growth of knowledge. A generation ago, the grouping of 

 floras and faunas found a ready explanation in differences 

 of climate and special creations. But no such easy solu- 

 tion of the difficulties now avails. Ever since the classic 

 essay of Edward Forbes on the history of the British 

 flora there has been a growing conviction that the present 

 arrangement of the life of the globe is the outcome of 

 previous geological and biological changes. The doctrine 

 of evolution has given to this conviction the strength of 

 demonstrated truth. But while the theoretical aspect of 

 the question may be clear enough, we are beset on all 

 sides by what seem utterly insuperable obstacles when 

 we try to work out the appUcation of this theory to the 

 history of any given flora or fauna. This is true even in 

 those areas of Europe and North America where the 

 living plants and animals are most fully known, and 

 where some approach to a complete unravelling of the 

 geological record has been made. But over most of the 

 rest of the globe our knowledge of botanical and zoologi- 

 cal distribution, and still more of geological history, is of 

 the scantiest and most fragmentary kind. A few broad 

 facts in the history of the mammalian life of the northern 

 hemisphere are well established. The pedigree of some 

 modern forms, such as the horse, can be traced back into 

 early Tertiary times ; the former wide spread of other 

 forms, the Uon for instance, and their gradual restric- 

 tion in area, have been satisfactorily made out. But 

 the kind of evidence available in these cases fails us 

 Vol. XXIII. — No. 590 



in dealing with others. It seems as if all that we may 

 hope to achieve is to establish by a few examples, capable 

 of clear proof, the general laws by which variation in 

 form and in geographical distribution appears to have 

 been efi'ected among the animal and vegetable populations 

 of the globe. 



By no living naturalist could these problems be more 

 fittingly and exhaustively discussed than by the author of 

 " The Malay Archipelago." Years of research in the East, 

 followed by years of research and reflection at home, have 

 enabled him to explore every highway and a vast number 

 of byways in the wide realm of inquiry in which he has 

 been so active and untiring a worker. Thoroughly con- 

 versant with all that has been done by others, he brings 

 to his task a wealth of information and a breadth of view 

 that stamp his works with the authority of a master. 



The present volume may be regarded as an expansion 

 of a part of the author's " Geographical Distribution of 

 Aniinals." Further study of the problem of distribution 

 has enabled him to treat it with greater fulness. He has 

 devoted especial attention to geological operations that have 

 affected the successive races of plants and animals, and 

 has connected these operations with biological changes 

 more closely and clearly than has hitherto been done. 

 Of his new volume the first half is mainly occupied with 

 a discussion of this subject. He there seeks to establish a 

 number of fundamental propositions or laws, the confirma- 

 tion of which leads in his opinion to a simpler and fuller 

 solution of the problem than has before been possible. 

 Two of these doctrines deserve the careful consideration 

 of geologists and naturalists. They are (i) the per- 

 manence of continental and oceanic areas ; and (2) the 

 frequency of changes of climate during geological time 

 and the combined influence of cosmical and geographical 

 causes in the production of these changes. 



The abundance of marine organisms in the rock-masses 

 which constitute the bulk of the continents naturally led 

 to a belief in the mutability of the land. Not once only 

 but many times in succession the sites of some of our 

 loftiest mountains were under the sea. And if it was 

 discovered that the position of the land had been so 

 variable, and that the sea-floor had been so continually 

 upraised, the inference was easily drawn that land and 

 sea must have been continually changing places. Tacitly 

 or explicitly it was assumed that just as there appeared 

 to be no area, even in the heart of the continents, which 

 had not been submerged beneath the waves, so there was 

 probably no tract even of mid-ocean where a continent 

 might not have bloomed. It is probably a safe assertion 

 to say that this is still the belief of most geologists. It finds 

 formal expression in their most authoritative text-books, 

 and can be traced everywhere in its influence upon the 

 discussion of questions of geological history. From 

 geological treatises it has passed out into the current 

 literature of the time, as one of the accepted conclusions 

 of science. Our Poet Laureate, who has embodied in 

 musical language not a little of the scientific speculation 

 of his day, has given terse expression to this universal 

 belief in the often-quoted lines : — 



" There rolls the deep where grevv' the tree. 

 O earth, what changes hast thou seen ! 

 There, where the long street roars, hath been 

 The stillness of the central sea." 



