574 



NA TURE 



[Oct. ii, 1883 



natural group of organisms at one time attributed to "conformity 

 to type," a so-called explanation which explained nothing, but 

 for which a vera causa may be found in descent from a common 

 ancestor. Wonderful gradations in the perfection to which 

 different structures have attained in the progress of their adapta- 

 tion to their respective purposes have also been shown, and of 

 still greater importance and interest, the numerous cases of 

 apparently useless or rudimentary organs in both animals and 

 plants, which were absolutely unaccounted for under the older 

 hypothesis. 



3. The comparatively new study of the geographical distribu- 

 tion of living things, which has only become possible since the 

 prosecution of the systematic and scientific explorations of the 

 earth's surface which have distinguished the present century. 

 Tiie results of this branch of inquiry alone have been sufficient 

 to convince many naturalists of the unsoundness of the old view 

 of the distinct origin of species, whether created each in the 

 region of the globe to which il is now confined, or, as many still 

 imagine, all in one spot, from « hich they have spread themselves 

 unchanged in form, colour, or other essential attributes to their 

 present abodes, however diverse in climate and other environ- 

 ments or conditions of existence. 



4. Lastly, though most important of all, must be mentioned 

 the entirely new science of palaeontology, opening up worl 

 organic life before unknown, also showing infinite gradations of 

 structure, but mainly important a, increasing our horizon of ob- 

 servation to an extent not previously dreamt of in the direction 

 of time. Powers of observation formerly limited to the brief 

 space of a few generations are now extended over ages, which 

 the concurrent testimony of various branches of knowledge, of 

 astronomy, cosmogony, and geology, show are immeasurable 

 compared with any periods of which we hitherto had cognisance. 

 We are enabled to trace, and every year, as discovery succeeds 

 discovery, with increasing distinctness, numerous cas 

 sequences of modification running through groups of animals in 

 successive periods of time, such as the gradual progress in the 

 development and perfection of the antlers of deer, from their 

 entire absence in the earliest known representative; of the type, 

 through the simple conical or bifurcated form, increasing in com- 

 plexity as time advanced to the magnificent many-branched ap- 

 pendages which adorn the heads of some species of recent stags ; 

 such also as the progressive modification, , so often described, 

 beginning in the short-necked, heavy-limbed, many-toed tapir- 

 like animal of the Eocene period, and ending in the graceful, 

 long-necked, light-limbed, single-toed horse of our own age, and 

 numerous others which time will not allow me even to mention. 



It would be impossible here to trace the history of the effect 

 of this enormous influx of knowledge upon the doctrine of the 

 separate origin and fixed characters of species ; to narrate the 

 scattered efforts of philosophical minds, discontented with the 

 former views, but not yet clearly seeing the light ; to describe 

 the slow and struggling growth of the new views, amid diffi- 

 culties arising from imperfections of knowle ige, and the opposi- 

 tion of prejudice, or to apportion to each of those who by their 

 labours have contributed to the final result his exact share in 

 bringing it about. How much, for instance, is due to the work 

 aud the writings of our illustrious countryman Darwin? and 

 haw much to tho^e who have preceded or followed him? All 

 this forms an episode in the history of the progress of human 

 knowledge which has been abundantly chro.iicled elsewhere. 



The result may, however, be briefly stated to be that the 

 opinion now almost, if not quite, universal among skilled and 

 thoughtful naturalists of all countries, and whatever their beliefs 

 upon other subjects, i s that the various forms of life which we 

 see around us, and he existence of which we know from their 

 fossil remains, are the product, not of independent creati ins, 

 but of descent, with gradual modification from pre-existing 

 f jrms. In short, the law of the natural descent of individuals, 

 of varieties, races, or breeds (which, being within the limits of the 

 previous powers of observation, was already universally admitted) 

 has been extended to the still greater modifications constituting 

 what we call species, and consequently to the higher groups 

 called genera, families, and orders. The barrier fancied to exist 

 between so-called varieties and so-called species has broken 

 down. 



Any one comnienciig the study of the subject at the present 

 time without prejudice, and carefully investigating the evidence 

 upon which to form his conclusions, bearing in mind that he 

 must look for his proofs, not so much in direct experiments or 

 absolute demonstrations, which from the nature of the case are 

 impossible, but in the convergence of the indications furnished 



by the interpretations of multitudinous facts of most diverse 

 kinds, must find it extremely difficult to place himself in the 

 position of those who held the older view, so much more reason- 

 » much more in accordance with all that we know of the 

 general phenomena of nature, does this new oiie seem. In fact 

 the onus probandi now appears entirely to lie with those who 

 make the assertion that species have been separately created. 

 Where, it may be asked, is the shadow of a scientific proof that 

 the first individual of any species has come into being without 

 pre-existing parents? Has any competent observer at any time 

 witnessed such an occurrence ? The apparent advent of a new 

 species in geological history, a common event enough, has cer- 

 tainly been cited as such. As well might the presence of a horse 

 in a field, with no sign of other animals of the same kind near it, 

 be quoted as evidence of the fallacy of the common view of the 

 descent of individuals. Ordinary observation tells us of the 

 numerous causes which may have isolated that horse from its 

 parents and kindred. Geologists know equally well how slight 

 the cha.ices of more than a stray individual or fragment of an 

 individual here and there being first preserved and afterwards 

 discovered to give any indication of the existence of the race. 

 Tho^e who object to the new view complain sometimes of the 

 frequency with which its advocates take refuge, as they call it, 

 in the " imperfection of the geological record." I think, on 

 the contrary, the difficulty is always to allow sufficiently for this 

 imperfection. When we contrast the ] resent know ledge of palce- 

 ontology with what it was fifty or even ten years ago ; when we 

 see by what mere accident, as it were, a railway driven through 

 a new country, a quarry worked fir commercial purposes, a city 

 newly fortified, all the most important discoveries of extinct 

 animals have been made, we must lie convinced that all argu- 

 ments drawn from the absence of the required links are utterly 

 valueless. The study of palaeontology is as yet in its merest 

 infancy ; the wonder is that it has already furnished so much, not 

 so little, corroboration of the doctrine of transmutation of 

 species. 



Direct proof is, then, equally absent from both theories. For 

 the old view it may be said that it has been held for a very long 

 time by persons whose knowledge of the facts of nature which 

 bear upon it was extremely limited. On the other hand, the 

 new view is continually receiving more support as that know- 

 ledge increases, and furnishes a key t< 1 a vat number of other- 

 wise inexplicable facts in every branch of natural history, in geo- 

 logical and geographical distribution, in the habits of animals, 

 in their development and growth, and es; ecially in their structure. 

 Allow me to take one instance from the la.- 1 named — the anatomy 

 of the whale. How is it possible, upon any other supposition 

 than that it is the descendant of some land animal, with com- 

 pletely developed limbs and teeth, which has become gradually 

 modified to suit an aquatic mode of existence, to explain the 

 presence of the numerous rudimentary, and to their present pos- 

 sessors absolutely useless, structures found in its body. Amongst 

 others, a complete set of teeth, existing only in embryonic life, 

 entirely disappearing even before birth, and rudimentary hind 

 legs, with their various bones, joints, and muscles, of which no 

 trace is seen externally. It may be asserted that the whale was 

 originally created so, as it was asserted, and long maintained, 

 that fossil shells and bones were originally created as such in the 

 rocks in which they are found. It took more than two centuries 

 of continuous and most acrimonious discussion to convince the 

 world, especially the theological world, that these were the 

 actual remains of animals which had .nice lived in a former 

 period of the earth's history. Their evidence is now, however, 

 universally admitted as supplying knowledge of the changed 

 conditions of the surface of the earth, and with equal clearness 

 do these rudimentary organs, hidden in the secret recesses of the 

 whale's body, furnish, to those wdio inquire, indications that the 

 animal has passed through phases of existence unlike those in 

 which we now see it. 



I do not for a moment assert that the new view explains 

 everything that we students of nature are longing to know, or 

 that we do not everywhere meet with obscure problems and 

 perplexing difficulties, facts that we cannot account for, and 

 breaks in the chain of evidence. As to the details and mode of 

 operation of the secondary laws by which variation and modifi- 

 cation have been brought about, we are far from being in accord. 

 Happy for us that it is so, or our work would be at an end. I 

 only maintain that the transmutation view removes more diffi- 

 culties, requires fewer assumptions, and presents so much more 

 consistency with observed facts than that which it seeks to super- 

 sede, and is, therefore, so generally accepted, that there is no 



