C.—GEOLOGY. 103 
us more complete and accurate knowledge than ever before. It may now 
be confidently stated that many of the most crucial links in the chain 
of evolving life are in our hands, that they actually lived in the past, 
and that their fossil forms show their relationship to their predecessors and 
successors. The time has come when Darwin’s famous chapter on the 
“Imperfection of the Geological Record,’ an apology written with the most 
balanced criticism and unbiassed judgment, should be rewritten and 
revised. 
It is true that we seem as far as ever from unveiling the points of 
divergence of the great phyla, and we can but feel that the time from the 
beginning of the Cambrian Period onward is but a small part of the whole 
history of life on the earth. As with antiquarian research, each new 
_ discovery in geology, whether on the physical or the biological side, only 
brings these distant ages more fully into view and emphasises their 
modernity and their likeness to our own time. Hutton’s famous dictum 
that he saw ‘ no vestige of a beginning, no prospect of an end,’ is to-day 
more true than ever, when we regard the evidence of stratified rocks. 
But we know enough to convince us that within post-Cambrian time 
evolution has steadily proceeded from general to special, from simple to 
complex, from lower to higher efficiency. 
In almost every subdivision of the animal kingdom, and in not a few 
branches of the vegetable kingdom, lines of descent and directions of 
specialisation have been made out, sometimes visibly operating through- 
out whole Systems, but more usually through smaller divisions of the 
record ; and this in the former kingdom not only among vertebrates but 
among the invertebrates and even their lower sub-kingdoms. It may 
_ even be stated that in methods of defence, in food-procuring in the attain- 
ment of favourable positions and attitudes, something very closely 
- imitating what would be expected on the doctrine of the origin of species 
by ‘ survival of the fittest ’ has again and again occurred. 
The essence of evolution is unbroken sequence, and when we consider 
the extraordinary delicacy of the adjustment of life to its physical and organic 
environment, the mutual interdependence of life forms, and the necessity to 
them of such factors as favourable range of temperature, food, climatic 
- conditions, soil, and the continuity of the ‘ element’ in or on which they 
_ live, it is most wonderful that in the vast lapse of post-Archzean time it has 
been possible for life to exist continuously, and continually to evolve, 
throughout those long ages. And this in spite of the fact that, although 
the main chain has been unbroken, conditions have, in many cases, been so 
unfavourable that whole groups have flourished and died out, while others 
have become so attenuated that only a few survivors have been left, highly 
restricted in distribution, to burgeon out again when the unfavourable 
conditions were removed, or in other places where conditions have again 
become more favourable to them. 
That life has survived continuously in spite of the vicissitudes through 
which it has been compelled to pass, and the frequent convergence upon it 
of unfavourable conditions, may well be taken to heart by those who fear 
that civilisation will be brought to an end by the misuse of the powers that 
itself has evolved. They may surely take courage and trust that the 
remedy for these evils will come, as it has in innumerable other cases, 
not from conventions and understandings that, as all history shows, will 
