,u 



NA TURE 



[August 9, 1894 



oculatioD against anthrax, hydrophobia, and perhaps some 

 other diseases, which we owe to Pasteur, must lie recorded as 

 splendid victories over the countless legions of our infinitesimal 

 foes. Results like these are the great glory of the scientific 

 worlicrs of the past century. Men may, perhaps, have o%-er- 

 rated the progress of nineteenth-century research in opening the 

 secrets of nature ; but it is difficult to overrate the brilliant 

 service it has rendered in ministering to the comforts and 

 diminishing the sufferings of mankind. 



If we are not able to see far into the causes and origin of life 

 in our own day, it is not probable that we shall deal more suc- 

 cessfully with the problem as it arose many million years ago. 

 Yet certainly the most conspicuous event in the scientific 

 annals of the last half-century has been the publication of Mr. 

 Darwin's work on the " Origin of Species," which appeared 

 in 1859. In some respects, in the depth of the impression 

 which It made on scientific thought, and even on the general 

 opinion of the world, its momentous effect can hardly be over- 

 stated. But at this distance of time it is possible to see that 

 some of its success has been due to adventitious circumstances. 

 It has had the chance of enlisting among its champions some 

 of the most powerful intellects of our time, and perhaps the 

 still happier fortune of appearing at a moment when it fur- 

 nished an armoury of weapons to men, who were not scien- 

 tific, for use in the bitter but transitory polemics of the day. 

 But far the largest part of its accidental advantages was to be 

 found in the remarkable character and qualifications of its 

 author. The equity of judgment, the simple-minded love of 

 truth and the patient devotion to the pursuit of it through years 

 of toil and of other conditions the most unpropitious^these 

 things endeared to numbers of men everything that came from 

 Charles Darwin, apart frnm its scientific merit or literary 

 charm. And whatever final value may be assigned to his doc- 

 trine, nothing can ever detract from the lustre shed upon it by 

 the wealth of his knowledge and the infinite ingenuity of 

 bis resource. The intrinsic power of his theory is shown 

 at least in this one respect, that in the department 

 of knowledge with which it is concerned it has 

 effected an entire revolution in the methods of 

 research. Before his time the study of living nature had a 

 tendency to be merely statistical ; since his time it has become 

 predominantly hi>torical. The consideration how any organic 

 t>ody came to be what it is occupies a far larger area in any 

 inquiry now than the mere description of its actual condition ; 

 but this question wasnot predominant — it may almost be said to 

 have been ignored — in the Botanical and Zoological study of 

 sixty years ago. 



Another lasting and unquestioned effect has resulted from 

 Darwin's work. He has, as a matter of fact, disposed of the 

 doctrine of the immutability of species. It has been mainly 

 associated in recent days with the honoured name of Ag.issiz, 

 but with him has disappeared the last defender of it who could 

 claim the attention of the world. Few now are found to doubt 

 that animals separated by differences far exceeding those that 

 distingui<.hed what we know as species have yet descended from 

 common ancestors. But there is much less agreement as to the 

 extent to which this common descent can be assumed, or the 

 process by which it has come about. Darwin himself believed 

 that all animals were descended from "al most (our or five pro- 

 genitors" — adding that "there was grandeur in the view that 

 Hie had been originally breathed by the Creator into a few 

 form or one." Some of his more devoted followers, like Prof. 

 Ilaeckel, were prepared to go a step farther and to contemplate 

 a ciyotal at the probable ancestor of the whole fauna and flora of 

 this planet. 



I'o inu extent the Darwinian theory h.is not effected the 

 conquest of Micniific opinion ; and still less is there any unanimity 

 in the acceptance ol natural (election as the sole or even the m.iio 

 agent uf whatever modifications may have led up to the exist- 

 ing formt of life. The deepest obscurity still hangs over the 

 oiigin of the infinite variety of life. Two of the strongest 

 objections to the Darwinian explanation appear still to retain 

 all their force, 



I think Lord Kelvin was the first lo point out that the 

 amount of lime required by the advocates of ihe theory for 

 working out the process they had in>agincd could not be con- 

 ccde<l without assuming the existence of a tr>tally different set 

 of natural laws from those with which we are ac'|uainled. His 

 view was not only b.iscd on profound mechanical reasoning, 

 but it was so plain that any layman could comprehend it. 



NO. 1293, VOL. 50] 



Setting aside arguments deduced from the resistance of 

 the tides, which may be taken to transcend the lay 

 understanding, his argument from the refrigeration of 

 the earth requires little science to apprehend it. 

 Everybody knows that hot things cool, and that according to 

 their substance they take more or less time in cooling. It is 

 evident from the incre.ase of heat as we descend into the earth, 

 that the earth is cooling, and we know by experiment, within 

 certain wide limits, the rate at which its substances, the 

 matters of which it is constituted, are found to cool. It 

 follows that we c.in approximately calculate how hot it was 

 i so many million years ago. But if at any time it 

 I was hotter at the surface by 50' 1". than it is now, 

 life would then have been impossible upon the 

 planet, and therefore we can without much diffi- 

 culty fix a date before which organic life on earth cannot 

 have existed. Basing himself on these considerations Lord 

 Kelvin limiied the period of organic life upon the earth to a 

 hundred million years, and Prof. Tail in a still more penurious 

 spirit cut that hundred down to ten. But on the other side of 

 the account stand the claims of the geologists and biologists. 

 They have revelled in the prodigality of the ciphers which they 

 put at the end of the eanh's hypothetical life. Long cribbed and 

 cabined within the narrow bounds of the popular chronology, 

 they have exulted wantonly in their new freedom. They have 

 lavished their millions of years with the open h.and of a prodigal 

 heir indemnifying himself by present extravagance for the en- 

 forced self.denial of his youth. But it cannot be gainsaid that 

 their theories require at least all this elbow-room. Ifwe think 

 of that vast distance over which Darwin conducts us from the 

 jelly-fish lying on the primeval beach lo man as we know him 

 now ; if we reflect that the prodigious change re<|uisile to trans- 

 form one into the other is made up of a chain of gener.ations, 

 each advancing by a minute variation from the form of its prede- 

 cessor, and if we further reflect that these successive changes are 

 so minute that in the course of our historical period — say three 

 thousand years — this |)rogressive variation h.as not advanced by 

 a single step perceptible to our eyes, in respect to man or the 

 animals and plants with which man is familiar, wc shall admit 

 that for a chain of change so vast, of which the smallest 

 link is longer than our recorded history, the biolo- 

 gists are making no extravagant claim when they demand 

 at least many hundred million years for the accomplish- 

 ment of the stupendous process. Of course, if the m.ithe- 

 maticians are right, the biologists cannot have what they 

 demand. If, for the purposes of their theory, organic life must 

 have existed on the globe more than a hundred million years 

 ago, it must, under the temperature then prevailing, have existed 

 , in a state of vapour. The jelly-fish would have been dissi- 

 I pated in steam long before he h.id had a chance of displaying 

 the advanlai;cous variation which was to make him the ancestor 

 of the human race. I see, in the eloquent discourse of one of 

 my most recent and most distinguished predecessors in this 

 chair, Sir Archibald Geikie, that the controversy is still 

 alive. The mathematicians sturdily adhere to their figures, 

 and the biologists are quite sure the mathematicians must have 

 made a mistake. I will not get myself into the line of fire l>y 

 intervening in such a controversy. But until it is adjusted the 

 laity may be excused for reluming a verdict of "nol proven" 

 upon the wider issues the Darwinian school has raised. 



The other objection is best st.ited in the words of an illus- 

 trious disciple of Darwin, who hits recently honoured this city 

 by his presence — I refer lo Prof Weismann. But in referring 

 to him, I cannot but give, in passing, a (eehle expression to the 

 universal sorrow wiih which in this place the news was received 

 that Weismann's distinguished antagonist, Prof. Uomancs, had 

 been taken from us in the outset and full promise of a splendid 

 scientific career. 



The gravest objection to the doctrine of natural selection was 

 expressed by Weismann in a paper published a few months ago, 

 not as agreeing to the objection, but as resisting it ; and there- 

 fore his language may be taken as an impartial statement of the 

 difficulty. " Wc accept natur.il selection," he says, "not 

 because we arc able to demonstrate the process in detail, not 

 even because we can with more or less ease imagine it, but 

 simply because wc must — because it is the only possible ex- 

 planation that wc can conceive. We must a.ssuiue natural 

 selection lo be the i>rinciple of the explanation of the metamor- 

 phoses, because all other apparent principles of explanation 

 fail us, and it is inconceivable that there could yet be another 



