468 



NATURE 



[Sept. 12, 1889 



under the conditions described above, and the remainder carefully 

 preserved in cabinets for the study of specialists. 



It is also very desirable in all museums, in order that the 

 exhibited series should be as little disturbed as possible in 

 arrangement, and be always available for the purpose for which 

 it is intended, that there should be, for the use of teachers and 

 students, a supplementary set of common objects, which, if in- 

 jured, could be easily replaced. It must not be forgotten that 

 the zealous investiga or and the conscientious curator are often 

 the direst antagonists : the one endeavours to get all the know- 

 ledge he can out of a specimen, regardless of its ultimate fate, 

 and even if his own eyes alone have the advantage of it ; the 

 other is content if a limited portion only is seen, provided that 

 can be seen by everyone both now and hereafter. 



Such, then, is the primary principle which ought to underlie 

 the arrangement of all museums — the distinct separation of the 

 two objects for which collections are made ; the publicly ex- 

 hibited collection being never a store-room or magazine, but 

 only such as the ordinary visitor can understand and profit by, 

 and the collection for students being so arranged as to afford 

 every facility for examination and research. The improve- 

 ments that can be made in detail in both departments are 

 endless, and to enter further into their consideration would lead 

 me far beyond the limits of this address. Happily, as I said 

 before, the subject is receiving much attention. 



I would willingly dwell longer upon it — indeed I feel that I 

 have only been able to touch slightly and superficially upon 

 many questions of practical interest, well worthy of more 

 detailed consideration— but time warns me that I must be 

 bringing this discourse to a close, and I have still said nothing in 

 reference to subjects upon which you may expect some words on 

 this occasion. I mean those great problems concerning the 

 laws which regulate the evolution of organic beings, problems 

 which agitate the minds of all biologists of the present day, and 

 the solution of which is watched with keen interest by a far 

 wider circle — a circle, in fact, coincident with the intelligence 

 and education of the world. Several communications con- 

 nected with these problems will be brought before the Sectional 

 meetings during the next few days, and we shall have the 

 advantage of hearing them discussed by some of those who by 

 virtue of their special attention to and full knowledge of these 

 subjects are most competent to speak with authority. It is 

 therefore for me rather delicate ground to tread upon, especially 

 at the close of a discourse mainly devoted to another question. 

 I will, however, briefly point out the nature of the problems and 

 the lines which the endeavour to solve them will probably take, 

 without attempting to anticipate the details which you will 

 doubtless hear most fully and ably stated elsewhere. 



I think I may safely premise that few, if any, original workers 

 at any branch of biology appear now to entertain serious doubt 

 about the general truth of the doctrine that all existing forms of 

 life have been derived from other forms by a natural process of 

 descent with modification, and it is generally acknowledged that 

 to the records of the past history of life upon the earth we must 

 look for the actual confirmation of the truth of a doctrine which 

 accords so strongly with all we know of the present history of 

 living beings. 



Prof. Huxley wrote in 1875 : — " The only perfectly safe found- 

 ation for the doctrine of evolution lies in the historical, or rathei 

 archaeological, evidence that particular organisms have arisen by 

 the gradual modification of their predecessors, which is furnished 

 by fossil remains. That evidence is daily increasing in amount 

 and in weight, and it is to be hoped that the comparisons of the 

 actual pedigree of these organisms with the phenomena of their 

 development may furnish some criterion by which the validity oi 

 phylogenic conclusions deduced from the facts of embryology 

 alone may be satisfactorily tested." 



Palaeontology, however, as we all know, reveals her seci'ets 

 with no open hand. How can we be reminded of this more 

 forcibly than by the discovery announced scarcely three months 

 ago by Prof Marsh of numerous mammalian remains from 

 formations of the Cretaceous period, the absence of which had 

 so long been a source of difficulty to all zoologists ? What vistas 

 does this discovery open of future possibilities, and what 

 thorough discredit, if any were needed, does it throw on the 

 value of negative evidence in such matters ! Bearing fully in 

 mind the necessary imperfection of the record we have to deal 

 with, I think that no one taking an impartial survey of the recent 

 progress of pal aeon tological discovery can doubt that the evidence 

 in favour of a gradual modification of living forms is still 



steadily increasing. Any regular progressive series of changes 

 of structure coinciding with changes in time can of course only 

 be expected to be preserved and to come again before our eyes 

 under such a favourable combination of circumstances as must 

 be of most rare occurrence ; but the links, more or less perfect, 

 of many such series are continually being revealed, and the 

 discovery of a single intermediate form is often of immense 

 interest as indicating the path along which the modification 

 from one apparently distinct form to another may have taken 

 place. 



Though palaeontology may be appealed to in support of the 

 conclusion that modifications have taken place as time advanced, 

 it can scarcely afford any help in solving the more difficult 

 problems which still remain as to the methods by which the 

 changes have been brought about. 



Ever since the publication of what has been truly described as 

 the "creation of modern natural history," Darwin's work on the 

 "Origin of Species," there has been no little controversy as to how 

 far all the modifications of living forms can be accounted for by 

 the principle of natural selection or preservation of variations 

 best adapted for their surrounding conditions, or whether any, 

 and if so what, other factors have taken part in the process of 

 organic evolution. 



It certainly cannot be said that in these later times the con- 

 troversy has ended. Indeed those who are acquainted with 

 scientific literature must know that notes struck at the last annual 

 meeting of this Association produced a series of reverberations, 

 the echoes of which have hardly yet died away. 



Within the last few months also, two important works have 

 appeared in our country, which have placed in an accessible and 

 popular form many of the data upon which the most prevalent 

 views on the subject are based. 



The first is, "Darwinism: an Exposition of the Theory of 

 Natural Selection, with some of its Applications," by Alfred 

 Russel Wallace. No one could be found so competent to give 

 such an exposition of the theory as one who was, simultaneously 

 with Darwin, its independent originator, but who, by the title he 

 has chosen no less than by the contents of the book, has, with 

 rare modesty and self-abnegation, transferred to his fellow- 

 labourer all the merit of the discovery of what he evidently looks 

 upon as a principle of overwhelming importance in the economy 

 of Nature ; "supreme," indeed, he says, "to an extent which 

 even Darwin himself hesitated to claim for it. " 



The other work I refer to is the English translation of the 

 remarkable "Essays upon Heredity and Kindred Biological 

 Problems," by Dr. August Weismann, published at the Oxford 

 Clarendon Press, in which is fully discussed the very important 

 but still open question — a question which was brought into 

 prominence at our meeting at Manchester two years ago — of the 

 transmission or non-transmission to the offspring of characters 

 acquired during the lifetime of the parent. 



It is generally recognized that it is one of the main elements 

 of Darwin's, as well as of every other theory of evolution, that 

 there is in every individual organic being an innate tendency to 

 vary from the standard of its predecessors, but that this tendency 

 is usually kept under the sternest control by the opposite ten- 

 dency to resemble them, a force to which the terms " heredity" 

 and " atavism " are applied. The causes of this initial tendency 

 to vary, as well as those of its limits and prevailing direction, 

 and the circumstances which favour its occasional bursting 

 through the constraining principle of heredity offer an endless 

 field for speculation. 1 hough several theories of variation have 

 been suggested, I think that no one would venture to say we 

 have passed beyond the threshold of knowledge of the subject 

 at present. 



Taking for granted, however, as we all do, that this tendency 

 to individual variation exists, then comes the question. What 

 are the agents by which, when it has asserted itself, it is con- 

 trolled or directed in such a manner as to produce the permanent 

 or apparently permanent modifications of organic structures which 

 we see around us? Is "survival of the fittest " or preservation 

 by natural selection of those variations best adapted for their 

 surrounding conditions (the essentially Darwinian or still more 

 essentially Wallacian doctrine) the sole or even the chief of 

 these agents ? Can isolation, or the revived Lamarckian view 

 of the direct action of the environment, or the effects of use or 

 disuse accumulating through generations, either singly or com- 

 bined, account for all ? or is it necessary to invoke the aid of any 

 of the numerous subsidiary methods of selection which have 

 been suggested as factors in bringing about the great result ? 



