290 



NATURE 



[September 2, 1909 



SECTION c. 



GEOLOGY. 



■Opening Address ey Arthur Smith Woodward, LL.D., 

 F.R.S., V.P.Z.S., Sec. G.S., Keeper of Geology in 

 THE British Museum, President of the Section. 



The circumstances of the present meeting very clearly 



■ determine the subject of a general address to be 

 expected from a student of extinct animals. The remark- 

 able discoveries of fossil backboned animals made on the 

 North American continent during the last fifty years sug- 

 gest an estimate of the results achieved by the modern 

 systematic methods of research ; while the centenary cele- 

 bration of the birth of Darwin makes it appropriate to 

 consider the extent to which we may begin deducing the 

 laws of organic evolution from the life of past ages as we 

 now know it. Such an address must, of course, be 

 primarily biological in character, and treat of some matters 

 which are not ordinarily discussed by Section C. The 

 subject, however, can only be appreciated fully bv those 

 who have some practical acquaintance with the limitations 

 under which geologists pursue their researches, and 

 especially by those who are accustomed to geological modes 

 of thought. 



There has been an unfortunate tendency during recent 

 years for the majority of geologists to relinquish the study 

 of fossils in absolute despair. More ample material for 

 ■examination and more e.xact methods of research have 

 altered many erroneous names which were originally used ; 

 while the admission to scientific publications of too manv 

 mere literary exercises on the so-called " law of priority " 

 has now made it necessary to learn not one, but several 

 names for some of the genera and species which are com- 

 monly met with. Even worse, the tentative arrangement 

 of fossils in " genetic scries " has led to the invention 

 of a multitude of terms which often serve to give a 

 sembla-nce of scientific exactitude to the purest guesswork, 

 and sometimes degenerate into a jargon which is naturally 

 repellent to an educated mind. Nevertheless, I still hope to 

 show that, with all these ditliculties, there is so much of 

 iundamental interest in the new work that it is worth 

 ■while to make an effort to appreciate it. Geology and 

 palaeontology in the past have furnished some of the 

 grandest possible contributions to our knowledge of the 

 •world of life ; they have revealed hidden meanings which 

 no study of the existing world could even suggest ; and 

 ihey have started lines of inquiry which the student of 

 living animals and plants alone would scarcely have sus- 

 pected to be profitable. The latest researches are the 

 logical continuation of this pioneer work on a more exten- 

 sive scale, and with greater precision ; and I am convinced 

 that they will continue to be as important a factor in the 

 progress of post-Darwinian biology as were the older 

 studies of fossils in the philosophy of Cuvier, Brongniart, 

 and Owen. 



In this connection it is necessary to combat the mistaken 

 popular belief that the main object of studying fossils is to 

 discover the " missing links " in the chain of life. We 

 are told that the idea of organic evolution is not worthy of 

 serious consideration until these li[iks, precise in character, 

 are forthcoming in all directions. Moreover, the critics 

 who express this opinion are not satisfied to consider the 

 simplest cases, such as are afforded by some of the lower 

 grades of " shell-fish " which live together in immense 

 numbers and have limited powers of locomotion. They 



■ demand long series of exact links between the most com- 

 plex skeletal frames of the backboned animals, which have 

 extreme powers of locomotion, are continually wandering, 

 and are rarely preserved as complete individuals when 

 they are buried in rock. They even expect continual dis- 

 coveries of links among the rarest of all fossils, those of 

 the higher apes and man. The geologist, on the other 

 hand, knowing well that he must remain satisfied with a 

 knowledge of a few scattered episodes in the history of life 

 which are always revealed by the merest accident, marvels 

 that the discovery of " missing links " is so constant a 

 feature of his work. He is convinced that, if circumstances 

 were more favourable, he would be able to satisfy the 



• demand of the most exacting critic. He has found enough 

 continuous series among the moUusca, for example, and 

 so many suggestions of equally gradual series among the 

 NO. 2079, VOL. Si] 



higher animals, that he does not hesitate to believe without 

 further evidence in a process of descent with modification. 

 The mere reader of books is often misled by the vagaries 

 of nomenclature to suppose that the intervals between the 

 links are greater than in reality ; but for the actual student 

 it is an everyday experience to find that fossils of slightly 

 different ages which he once thought distinct are linked 

 together by a series of forms in which it is difficult to 

 discover the feeblest lines of demarcation. He is therefore 

 justified in proceeding on the assumption that in all cases 

 the life of one geological period has passed by a natural 

 process of descent into that of the next succeeding period ; 

 and, avoiding genealogical guesswork which proves to be 

 more and more futile, he strives to obtain a broad view of 

 the series of changes Nyhich have occurred, to distinguish 

 between those which denote progress and those which lead 

 to stagnation or extinction. When the general features of 

 organic evolution are determined in this manner, it will be 

 much easier than it is at present to decide where missing 

 links in any particular case are most likely to be found. 



.Among these general features which have been made 

 clear by the latest systematic researches, I wish especially 

 to emphasise the interest and significance of the persistent 

 progress of life to a higher plane, which we observe during 

 the successive geological periods. For I think palaeontolo- 

 gists are now generally agreed that there is some principle 

 imderlying this progress much more fundamental than 

 chance-variation or response to environment however much 

 these phenomena may have contributed to certain minor 

 adaptations. Consider the case of the backboned animals, 

 for instance, which I happen to have had special oppor- 

 tunities of studying. 



We are not likely ever to discover the actual ancestors 

 of animals on the backboned plan, because they do not 

 seem to have acquired any hard skeleton until the latter 

 part of the Silurian period, when fossils prove them to 

 have been typical and fully developed, though low in the 

 backboned scale. The ingenious researches and reasoning 

 of Dr. W. H. Gaskell, however, have suggested the pos- 

 sibility that these animals originated from some early 

 relatives of the scorpions and crustaceans. It is therefore 

 of great interest to observe that the Eurypterids and their 

 allies, which occupy this zoological position, were most 

 abundant during the Silurian period, were represented by 

 species of the largest size immediately afterwards at the 

 beginning of the Devonian, and then gradually dwindled 

 into insignificance. In other words, there was a great 

 outburst of Eurypterid life just at the time when back- 

 boned animals arose ; and if some of the former were 

 actually transformed into the latter, the phenomenon took 

 place when their powers both of variation and of multiplica- 

 tion were at their maximum. 



Fishes were already well established and distributed over 

 perhaps the greater part of the northern hemisphere at the 

 beginning of Devonian times ; and then there began sud- 

 denly a remarkable impulse towards the production of 

 lung-breathers, which is noticeable not only in Europe and 

 North America, but also probably so far away as .Aus- 

 tralia. In the middle and latter part of the Devonian 

 period, most of the true fishes had paddles, making them 

 crawlers as much as swimmers ; many of them differed from 

 typical fishes, while agreeing with lung-breathers, in having 

 the basis of the upper jaw fused with the skull, not sus- 

 pended ; and some of them exhibited both these features. 

 Their few survivors at the present day (the Crossoptery- 

 gians and Dipnoans) have also an air-bladder, which might 

 readily become a lung. The characteristic fish-fauna of 

 the Devonian period, therefore, made a nearer approach to 

 the land animals than anv group of fishes of later date ; 

 and it is noteworthy that in the Lower Carboniferous of 

 .Scotland — perhaps even in the Upper Devonian of North 

 .America, if footprints can be trusted — amphibians first 

 appeared. In L'pper Carboniferous times they became 

 firmly established, and between that period and the Trias 

 thev seem to have spread all over the world ; their remains 

 having been found, indeed, in Europe, Spitsbergen, India, 

 South .Africa, North and South .America, and .Australia. 



The Stegocephala or Labyrinthodonts, as these primitive 

 amphibians are termed, were therefore a vigorous race ; 

 but the marsh-dwelling habits of the majority did not allow 

 of much variation from the salamander-pattern. Only in 

 L'pper Carboniferous and Lower Permian times did some 



