4IO 



NA TURE 



[March 5, 1896 



Brown-Sequard's experiments, it will be seen that I have 

 not been able to furnish any approach to a full cor- 

 roboration. But I must repeat that my own experiments 

 have not as yet been sufficiently numerous to justify me 

 in repudiating those of his statements which I have not 

 been ably to verify" (p. 122). 



The second section of the work deals with " Utility," 

 and opens with the contention already familiar in the 

 author's earlier writings, that natural selection is not a 

 theory of the origin of species, but of the origin of 

 adaptations. The discussion throughout this section is 

 of great interest, although perhaps somewhat too con- 

 troversial in tone ; but this is a consequence of previous 

 controversies on the same subject. The effect of con- 

 troversy here, as in other cases, is to emphasise the 

 differences of opinion. The present writer ventures to 

 think that if this question of the utility of specific 

 characters were treated less controversially and more by 

 the discussion of particular examples, very little differ- 

 ence of opinion would be found to exist. The essence 

 of the question is contained in the definition of the term 

 " specific character," and this again depends on the 

 definition of the term " species." But we know that no 

 satisfactory, viz. generally applicable, objective definition 

 of species can be given, inasmuch as the subjective 

 ideas of the species describer have been of pre-eminent 

 importance. 



In certain classes of cases the species describer has, 

 and obviously correctly, made adaptive characters his 

 criteria ; for instance, in the species of Ranunculus alluded 

 to by Mr. Thiselton-Dyer in his discussion of this question, 

 as President of Section D, at Bath (British Association 

 Reports, p. 692). Of the opposite kind are the various 

 representative races or species which we meet as we 

 trace the distribution of numerous forms of life over 

 the earth's surface, and which afe especially well 

 seen in the Heliconine Danainas from tropical America, 

 in the Godman-Salvin Collection. Following one of 

 these forms in its range we find, in numerous cases, 

 that different areas are characterised by differences 

 in the colours and markings of the wings. The 

 colours and markings themselves are believed by many 

 to be adaptive, and to be of value for the purposes of 

 warning ; but the local differences alluded to cannot be 

 explained in this way, except in the cases of mimicry 

 between local forms. Assuming the received explanation 

 to be correct, natural selection would appear to have 

 operated only in preventing the local differences from 

 diminishing the efficiency of the warning character. But 

 these local forms of colouring and marking are made the 

 criteria — and are, indeed, apparently the only criteria— 

 of specific distinction in numberless cases. It may be 

 that, in many of these cases, future investigation will 

 prove a biological continuity of the forms over the whole 

 of the range, so that the names which are now applied to 

 species will have to be used for geographical races. In 

 the interests of biological science it is necessary that 

 the naming of different forms should proceed at a much 

 faster rate than the scientific proof of specific rank : in- 

 deed, the latter must, in the majority of cases, be a very 

 slow and arduous process. Much confusion and contro- 

 versy would be avoided if describers were clearly to state, 

 as regards a large proportion of the forms described 

 NO. 1375, VOL. 53] 



every day, that specific rank is only provisionally claimed. 

 There is abundant justification for conferring a name, 

 or a number, or some kind of ticket, upon every clearly 

 marked form, quite apart from the question of its 

 specific rank. 



It therefore follows that this controversy must be a 

 barren one as regards a very large proportion of the 

 forms which are now distinguished as species, especially 

 in groups like the Insecta, in which such forms are 

 most numerous. AmoYig the cases in which specific 

 rank is indisputable, it can hardly be maintained that 

 all the superficial differences between two allied species 

 which have resulted from separation on the opposite 

 sides of some geographical barrier, are necessarily 

 adaptive. 



This work, like all the writings of its author, is sure 

 to appeal to a wide circle of readers, and will be of high 

 value in bringing before the public the discussion, by an 

 exceptionally acute thinker, of some of the most disputed 

 and difficult points in modern theories of evolution ; 

 while biological science cannot fail to gain by the 

 attention directed to the need for further observation 

 and experiment in order that a final decision may be 

 reached. E. B. P. 



COMPLETION OF THE ''INDEX- 

 CATALOGUE." 

 Index-Catalogue of the Library of the Surgeon-GeneraV s 

 Office, United States Army. Authors and Subjects. 

 Vol. xvi. W — Zythus. Folio, pp. xiv. -f [282] -4- 822. 

 (Washington : Government Printing Office, 1895.) 



THIS sixteenth volume completes the twenty years' 

 labour of Dr. J. S. Billings, and brings the 

 catalogue of the finest medical library in the world to 

 the close of the alphabet. We have in previous articles 

 remarked on its extraordinary fulness, and its value to 

 all engaged in the study of medical literature. For it 

 is not merely a guide to the Washington Library ; it is 

 a classified index to something like a moiety of all 

 that has ever been published on medicine and its allied 

 sciences. Ample and distinctive descriptions are given 

 of more than 300,000 books and articles, with over 800,000 

 cross-references. The volume before us has an addi- 

 tional feature of the greatest usefulness. No less than 

 282 folio pages are required to contain a Hst of the abbre- 

 viated and the complete titles of the periodicals, trans- 

 actions, reports, and the like, now or formerly issued 

 in all parts of the world and in every civilised language. 

 The abbreviations are those used in the catalogue ; but 

 they are so concise, and at the same time so sufficient, 

 that it would be well if they could be uniformly adopted 

 by all who quote — and give their authority. 



The recent international testimonial to Dr. Billings, 

 and the public banquet at which, with his fellow-workers, 

 Dr. Chadwick, of Boston, and Dr. Fletcher, originally 

 of Bristol, he was a few weeks ago honoured in Phila- 

 delphia, have furnished some indication of the wide- 

 spread feeling of grateful admiration his great enterprise 

 has evoked among his medical and scientific brethren. 

 The feeling has found stately expression in the Latin 

 diploma whereby an honorary doctorate was conferred 

 by the University of Munich on the Surgeon-General : 



