NATURE 



\May 6, 1880 



tants of the world, and at each successive period between 

 the extinct and still older species, why is not every geo- 

 loo-ical formation charged with such links? Why docs 

 not every collection of fossil remains afford plain evidence 

 of the gradation and mutation of the forms of life ? We 

 meet wTth no such evidence, and this is the most obvious 

 and plausiblelof the many objections which may be urged 

 against my theory." ^ 



Nothing could have been more useful to the opposition 

 than this characteristically candid avowal, twisted as it 

 immediately was into an admission that the writer's views 

 were contradicted by the facts of paleontology. But, 

 in fact, Mr. Darwin made no such admission. What 

 he says in effect is, not that palsontological evidence is 

 against him, but that it is not distinctly in his favour ; 

 and without attempting to attenuate the fact, he accounts 

 for it by the scantiness and the imperfection of that 

 evidence. 



What is the state of the case now, when, as we have 

 seen, the amount of our knowledge respecting the mam- 

 malia of the Tertiary epoch is increased fifty-fold, and in 

 some directions even approaches completeness ? 



Simply this, that if the doctrine of Evolution had not 

 existed paleontologists must have invented it, so irresist- 

 ibly is it forced upon the mind by the study of the remains 

 of the Tertiary mammalia which ha\'e been brought to 

 light since 1859. 



Among the fossils of Pikermi, Gaudry found the suc- 

 cessive stages by which the ancient civets passed into the 

 more modern hyajnas ; through the Tertiary deposits of 

 Western America, Marsh tracked the successive forms by 

 which the ancient stock of the horse has passed into its 

 present form ; and innumerable less complete indications 

 of the mode of evolution of other groups of the higher 

 mammaha ha\'e been obtained. 



In the remarkable memoir on the Phosphorites of 

 Ouercy, to which I have referred, M. Filhol describes no 

 fewer than seventeen varieties of the genus Cynodicfis, 

 v.-hich fill up all the interval between the viverine animals 

 and the bear-like dog Amphicyonj nor do I know any 

 solid ground of objection to the supposition that in this 

 Cynodictis-AmpMcyon group we have the stock whence 

 all the Viveridse, Felidse, HyasnidK, Canidas, and perhaps 

 the Procyonidae and Ursida;, of the present fauna have 

 been evolved. On the contrary, there is a great deal to 

 be said in its favour. 



In the course of summing up his results, M. Filhol 

 observes ^ : — 



" During the epoch of the phosphorites, great changes 

 took place in animal forms, and almost the same types as 

 those which now exist became defined from one another. 

 " Under the influence of natural conditions of which 

 we have no exact knowledge, though traces of them are 

 discoverable, species have been modified in a thousand 

 ways : races have arisen which, becoming fixed, have 

 thus produced a corresponding number of secondary 

 species." 



In 1S59, language of which this is an unintentional 

 paraphrase, occurring in the "Origin of Species," w^as 

 scouted as wild speculation ; at present, it is a sober state- 

 ment of the conclusions to which an acute and critically- 

 minded investigator is led by large and patient study of 

 the facts of palajontology. I venture to repeat what I 

 have said before, that, so far as the animal world is con- 



I " Origin of Species, cd. i. p. 463. 



-" This passage was omitted in the delivery of the lecture. 



\ 



cerned. Evolution is no longer a speculation, but a state- 

 ment of historical fact. It takes its place alongside of 

 those accepted truths which must be taken into account 

 by philosophers of all schools. 



Thus when, on the first day of October next, the " Origin 

 of Species" comes of age, the promise of its youth will be 

 amply fiulfiUed ; and we shall be prepared to congratulate 

 the venerated author of the book, not only that the 

 greatness of his achievement and its enduring influence 

 upon the progress of knowledge have won him a place 

 beside our Harvey; but, still more, that, like Harvey, he ) 

 has lived long enough to outlast detraction and opposition, 

 and to see the stone that the builders rejected become 

 the head-stone of the corner. T. H. HuxLEY 



ON MULTIPLE SPECTRA 



" Nunc age, quo motu genitalia material 



Corpora res varias gignant, genitasque resolvant 

 Et qua vi facere id cogantur." 



Lucretius, ii., 61-2. 



" Prima moventur euim per se primordia rerum : 

 Inde ea, quae pan-o sunt corpora conciliatu, 

 Et quasi proxima sunt ad vireis principiorum, 

 Ictibus illoram caecis impiilsa cientur 

 Ipsaque, qua; porro paulo maiora, lacessunt." 



Liicrdiiis, ii. 132-6. 



"It is conceivable that the various kinds of matters, nowj 

 recognised in different elementary substances, may possess one , 

 and the same ultimate or atomic molecule existing in different 1 

 conditions of movement. 



" The essential unity of matter is an hypothesis in harmony: 

 with the equal action of gravity upon all bodies." — Graham's 

 Researches, p. 299. 



IN a recent paper ' I showed that a study of the minutel 

 anatomy of spectra, both terrestrial and celestial,^ 

 forces upon us the conclusion that both in the electric, 

 arc and in the hottest region of the sun the ^o-calledi 

 chemical elements behave after the manner of compound' 

 bodies. 



I then dealt more especially with the question of the 

 basic lines in the various spectra, and it is clear that if> 

 at any one temperature, there be some lines only truly 

 basic in the spectrum of any element, we at once divide the j 

 lines visible at that temperature into two groups, those! 

 which are basic and those which are not. This would 

 o-ive a compound origin to the lines, and this is the real 

 point. 



It is now years ago since the view was first held thai 

 the elementary bodies had double spectra, that is, thai 

 each, or at all events several, under changed conditions 

 of temperature or electric tension, gave us now a flutec 

 spectrum and now one composed of lines. 



I glimpsed the idea some time afterwards that the line 

 spectrum was in its turn in all probability a comple> 

 whole, in other words that it was the summation of th« 

 spectra of various molecular groupings. 



Recent work has to my mind not only shown that this 

 is true, but that in the case of many bodies the complexity 

 and therefore the number, of the molecular groupings whicl 

 give rise to that compound whole called a line spectrum 

 is considerable. 



It is therefore important from my point of view to re 

 consider the evidence on which the assertion that th( 

 New Departure in Spectrum Analysis' 



^ *' On the Necessity for 

 (Nature, vol. -i.ti. p. 8). 



