Nov. 9, 1 871] 



NATURE 



;5 



of species. He says : — " Every true species presents in its 

 individuals certain features, specific characters, which distinguish 

 it from every otlier species : as if the Creator had set an exclusive 

 mark or seal on each type." He likewise believed in specific 

 centres of distribution. He held that all the individuals 

 composing a species had descended from a single progenitor, 

 or from two, according as the sexes mij^iht be united or 

 distinct, and that, consequently, the idea of a species involved 

 the idea of the relationship in all the individuals of common 

 descent ; and ihe converse, that there could by no possibility be 

 community of descent except in living beings which possessed 

 the same specific characters. He supposed tnat the original in- 

 dividual or pair was created at a particular spot where the con- 

 ditions were suitable lor its existence and propagation, and that 

 the species extended and migrated frum that spot on all sides, 

 over an area of greater or less extent, until it met with some 

 natural barrier in the shape cf unsuitable conditions. No specific 

 form could have more than a single cen-re of distribution. II its 

 area appeared to be broken uii, a patch not in connection with 

 the originil centie of distribution occurring in some distant 

 locality, it was accounted for by the formation, through some 

 geological change, after the first spread of the species, of a 

 bairicr which cut off part of its area, or by some accidental 

 transport to a place where the conditions were sufficiently similar 

 to those of its original habitat to enable it to become naturali.^ed. 

 No species once exienninated was ever re-created, so that in 

 those lew cases in which we find a species abundant at one period 

 over an area, absent over the same area for a time, and recurring at 

 a later period, it must be accounted for by a change in the con- 

 ditions of the area which forced the emigration of the species, and 

 a subjequent furlher change which permitted its return. Forbes 

 defined and advocated what he called the law of " representation." 

 He found that in all parts of the world, however far removed, and 

 however completely separated by natural barriers, where the con- 

 ditions of life are similar, species, and groups of species, occur, 

 which, alihough not identical, resemble one another very closely ; 

 and he found that this similarity existed likewise between groups 

 of fossil remains and between groups of fossils and groups 

 of recent forms. Admitting the constancy of specific characters, 

 these resemblances could not be accounted for by community of 

 descent, and he thus arrived at the generalisation that in localities 

 placed under similar circumstances, similar, though specifically 

 distinct, specific forms were created. These he regarded as mu- 

 tually representative species. Our acceptance of the doctrines of 

 " specific centres " and of "rrpresentation," or at all events the 

 form in whi^hwe may be inclined to accept them, depends greatly 

 upm the acceptance orrejection of ihe fundamental dogma of the 

 immutability of species, and on this point theie has been a 

 very great change of opinion within the last ten or twelve 

 yea^^ — a change certainly due to the remarkable ability and 

 candour with which the question has been discussed by Mr. 

 Darivin and Mr. Wallace. I do not think that I am speak- 

 ing too strongly when I say that there is now scarcely a single 

 competent general naturalist who is not prepared to accept 

 some form of the doctrine of evolution. 'I here are no doubt 

 very great difiiculties in the minds of many of us in conceiv- 

 ing that, commencing from the simplest living being, the present 

 state of things in the organic world has been produced solely by 

 the combined action of "atavism," ihe tendency of offspring to re- 

 semble their parents closely, and "variation," the tendency of off- 

 spring to differ individually from their parents within very narrow 

 limits ; and many are inclined to believe that some law, as yet 

 undiscovered, oiher than the "survival of the fittest" must re- 

 gulate the existing marvellous s\stem of extreme and yet har- 

 monious modification. Still, it must be admitted that variation 

 is a vera causa, probably capable, within a limited period, under 

 favourable circumstances, of convcr ing one species into what, 

 according to our present ideas, we should be forced to recognise 

 as a different species ; and such being tlie case, it is perhaps con- 

 ceivable that duiing the lipse ot a period of time — still mfiniiely 

 shorter than eteriity — variation may have produced the entire 

 result. The individuals composing a species have a definite 

 range of vaiiation strictly limiied by the circumstances under 

 which the group of indiwduals is placed. Except in man and 

 in domesticated animals, in which it is artificially incre.ised, this 

 iniiividuil variaiii.n is u^uahy so t-light as to be inappreciable 

 except to a pracii-ed eye ; and any txtreme variation which 

 passes the natural limit in any direction clashes in sume way 

 with sur.ounding circumstances, and is dangerous to the life of 

 the individual. The normal or graphic line, or "line of safety," 



of the species, lies midway between the extremes of variation. 

 If at any period in the history of a species, the cmditions of life 

 of a group of individuals of the species are gradually altered ; 

 with the gtadual change of circumstances the limit of variation is 

 contracted in one direction and relaxed in another, it becomes 

 more dangerous to diverge towards one side, and more desir- 

 able to diverge towards the other, and the position of the 

 lines limiting variation is altered. The normal line, the line 

 along which the specific characters are most strongly marked, is 

 consequently slightly deflected, some characters being more 

 strongly expressed at the expense ot others. This deflection, 

 carried on for ages in the same diection, must eventually 

 carry the divergence of the varying race far beyond any 

 limits within which we are in the habit of admitting identity of 

 species. But the process must be, so to speak, infinitely slow. 

 It is difficult to form any idea of ten, fifty, or a Imndred millions 

 of years ; or of the relation which such periods bear to changes 

 taking place in the organic world. We must remember, how- 

 ever, that the rocks of the Silurian system, overlaid by ten miles 

 thickness of sediment, entombing a hundred successive faunre, 

 each as rich and varied as that of the present day, are themselves 

 teeming with fossils fuliy representing all the existing classes of 

 animals except the very highest. If it is possible to imagine 

 that this marvellous manifestation of eternal power and wisdom 

 involved in living nature can have been worked out through the law 

 of "descent with modification " alone, we shall certainly require 

 from the physicists the very longest row of cyphers which they 

 can afford. Now, although the admission of adoctiine of 

 evolution must affect greatly our conception of the origin and 

 rationale oi so-called specific centres, it does not practically affect 

 the question of their existence, or of the laws regulating the 

 distribution of species from these centres by migration, by 

 transport, by ocean currents, by elevations or depressions of the 

 land, or by any other causes at work under existing circumstances. 

 So far as practical naturalists are concerned, species are per- 

 manent within their narrow limits of variation, and it would 

 introduce an element of infinite confusion and error if we were to 

 regard them in any other light. The origin of species by 

 "descent with modification " is as yet only a hypothesis. During 

 the whole period of recorded human observation, not one single 

 instance of the change of one species into another has been 

 detected, and, singular to say, in successive geological formations, 

 although new species are constantly appearing, and there is 

 abundant evidence of progressive change, no single case has as 

 yet been observed of one species passing through a series of 

 inappreciable modifications into another. 



ON THE OBJECTS AND MANAGEMENT OF 

 PRO VI NCI A L MUSE UMS * 



A LTHOUGH every intelligent person knows more or less 

 -^ what these institutions are, and what they ought to be, 

 there is probably no subject, connected with the modern means 

 of education in natural science, concerning which so much mis- 

 conception or ignorance is manifested and tolerated as in the 

 Management and Objects of our Provincial Museums. The ma- 

 jority of them throughout England present such examples of 

 helpless misdirection and incapacity as could not be paralleled 

 elsewhere in Europe. Some noteworihy exceptions there are. 

 But generally the managers or guardians of local museums are 

 precisely of this unfit class, and seem to have no more notion of 

 their char.e than as mere curiosity-shops, and even display less 

 intelligence than is shown in such shops, where the cupidity or 

 shrewdness of the dealer induces him at least to take due care of, 

 and give a local habitation and a name to, his wares. But in the 

 provincial museums even this care and tittle of information is per- 

 tinaciously withheld, and the visitors are left to do the best they 

 can amid the surrounding bewilderment. This is commonly 

 made up of a most puzzling jumble of heterogeneous miscella- 

 nies, arranged, or rather scattered, with an equally sovereign 

 contempt for the convi-nience or instruction of the public, and 

 indeed all in such admired disorder as may most plainly show- 

 how Chaos is come again and Confusion can make his master- 

 piece, and how every specimen added to the heap only tends to 

 increase or perpetuate the miserable derangement. It looks as 



* Abstract of .in Address to a Meeting of the East Kent Natural History 

 Society, at Canterbury. Oct 12, 1871, by its Vice-President and Honorary 

 Secretary, George Gulliver, F. R.S. 



