48o 



NATURE 



[June S, iqi i 



initial stages and advance quickly to simplfc ridrr 

 work. There are four main sections in the book; 

 each of these starts with an experimental investiga- 

 tion and ends with the theoretical treatment of the 

 corresponding theorems. There are abundant 

 numerical examples, but sonie teachers will consider 

 that the sunply of riders is inadequate. An excellent 

 innovation is the insertion of circle properties before 

 areas are dealt with. This provides such an excel- 

 lent field of simple and interesting riders that it is 

 surprising that the Euclidean order has been followed 

 so long. The last section contains as many of the 

 theorems on ratios as are usually given in elemen- 

 tary text-books, the numerical examples, illustrating 

 the use of proportion, are particularly good. 



(4) The analytical geomelrv of the conic is treated 

 in this volume in less detail than is usual in most 

 text-books. For practical purposes, it is far more 

 important for the student to acquire a correct appre- 

 ciation of the principles which obtain for curves of 

 any degree, and to master the use of infinitesimal 

 methods. The author has therefore employed the 

 calculus freely and applied it both to plane and skew 

 curves and simple surfaces. The examples have been 

 chosen rather to elucidate principles than to test 

 analytical dexterity. The book may be used with 

 confidence by engineering students, with whose needs 

 it is primarily concerned. 



SCIENCE AXD SPECULATION. 

 The World of Life: a Manifestation of Creative 

 Power, Directive Mind, and Ultimate Purpose. By 

 Dr. A. R. Wallace, F.R.S. Pp. xvi + 4o8. 

 (London : Chapman and Hall, Ltd., 1910.) Price 

 12s. 6d. net. 



'T'HE appearance of a new book written by the 

 1 veteran naturalist in his eighty-eighth year can- 

 not fail to arouse the interest of a wide circle of 

 readers. The work may indeed be regarded as a 

 recapitulation of the opinions on a great variety of 

 topics which, during a long and active literary career, 

 extending over more than fifty years, Dr. Alfred Russei 

 Wallace has put forth in a number of memoirs, books, 

 and magazine articles. But to regard the work as a 

 mere summary of the results of former labours would 

 be to do a great injustice to its author; for there is 

 scarcely a subject referred to in it, in which fresh facts, 

 novel lines of reasoning, or suggestive conclusions are 

 not presented for our consideration. 



The book naturally divides itself into two portions, 

 which are of very diverse character and unequal value 

 and importance. As regards the first part, we must 

 state at once that the space at our disposal is alto- 

 gether insufficient to enumerate— much less to discuss 

 — the numerous interesting problems suggested in it. 

 After a first chapter, devoted to a somewhat 

 academical discussion of the nature and origin of 

 life, we have five chapters treating on the subject with 

 which Dr. Wallace's name will always be so honour- 

 ably associated— the distribution of plants and 

 animals. Readers familiar with the author's great 

 work on this subject, and with his "Island Life," 

 will be surprised and delighted to find how many 

 NO. 2 171, VOL. 861 



novel facts and lines of treatment have suggested 

 themselves to the author since the publication of hi^ 

 earlier works. Among many interesting discussions 

 in this part of the book we may specially instance 

 the contrasts pointed out between the more uniform 

 floras of temperate climes and the richly diversified 

 floras of tropical lands. These latter are shown in 

 many cases to be in great danger of extinction through 

 human agencies, and the interesting suggestion is 

 made that the British Government might follow the 

 example of the Dutch in Java, by establishing small 

 forest reserves in our tropical colonies; such reserves, 

 Dr. Wallace points out, need not be of anything like 

 the extent of the animal reservations of North .America 

 and .Africa, for, owing to the crowded and diversified 

 nature of all parts of a tropical forest, small areas of 

 even a square mile would be suftlcient for the purpose. 



Later chapters devoted to illustrations, extensions, 

 and new applications of the theory of natural selec- 

 tion cannot fail to arrest the attention of all 

 naturalists ; we may especially refer to the discus- 

 sion of " recognition marks," and those on bird life, 

 bird migration and extinction, and the relations of 

 bird to insect life. We may note that even when the 

 author feels compelled to express dissent from the 

 views of Darwin — as in his ideas concerning the origin 

 of man's intellectual and moral faculties — we find his 

 loyalty and devotion to his old friend and fellow- 

 worker displayed as conspicuously as ever. 



The three chapters on the geological record, well 

 illustrated as they are by wood-cuts drawn from various 

 sources, abound with interesting observations. We 

 may instance his development of the ideas put for- 

 ward by Dr. Smith Woodward, in an address to the 

 British Association, concerning the tendency of groups 

 of animals in the periods before their final extinction 

 to run into extravagant and sometimes bizarre forms. 

 This is illustrated in the case of the trilobites and 

 ammonites. 



Later chapters on the relations of the chemical 

 elements to vital agencies, on the " mystery of the 

 cell," on the parts played by plants, animals, and 

 man respectively in the economy of nature, are elo- 

 quent and illuminating; but it is unfortunate that 

 the author is never able to avoid the pitfalls of Ideo- 

 logical speculation. This tendency is still more 

 strikingly manifested when the author proceeds to 

 discuss such questions as the existence of pain in the 

 lower animals, of the non-justifiability of vivisection, 

 of the remedies for the overcrowding of cities, and 

 similar problems of the day. On all these and 

 similar questions Dr. Wallace writes very confidently, 

 sometimes intruding his speculative opinions in the 

 midst of the treatment of purely scientific questions. 



Most of the author's scientific friends — and they 

 are very numerous — will feel regret that these and 

 similar discussions were not reserv'ed for a separate 

 volume. We are all familiar, from reading his " Man's 

 Place in the L^niverse," and his autobiographical 

 work — " My Life " — with the author's peculiar 

 views on e.vtra-scientific, social, and political questions. 

 Some of these tendencies to unbridled speculation seem 

 to have reached an extreme limit in the twilight of 

 a noble life, as when it is gravely suggested to sub- 



