PRESIDENTIAL ADDRESS. 465 
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 links, 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 complex 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 discoveries 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 mollusca, for 
example, and so many suggestions of equally gradual series among the 
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 they are 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 which 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 paleontolo- 
gists are now generally agreed that there is some principle underlying 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 opportunities 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 back- 
boned scale. The ingenious researches and reasoning of Dr. W. H. Gaskell, 
however, have suggested the possibility 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 insignifi- 
