CXviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [May I909, 



The most direct evidence as to the general course of evolution in 

 the organic world is afforded by fossils, and enboldened by this 

 some geologists have proceeded to pronounce judgement on a 

 question which, some may think, lies altogether outside the range 

 of our enquiries. This question is the controversy of contro- 

 versies, popularly symbolized by the opposing doctrines of Lamarck 

 and Darwin. The fundamental problem which underlies the whole 

 study of evolution is without doubt that of variation ; yet how 

 slight is our knowledge, or rather how dense is our ignorance 

 concerning this question ! We know nothing as to its causation 

 and very little as to its laws ; and, as regards its efficiency in the 

 production of species, we cannot assert positively whether it is 

 continuous or discontinuous or both : doubts may even be enter- 

 tained, as to how far it is determinate or indeterminate. 1 Geology 

 •can scarcely be expected to answer these questions ; but there are 

 others, directly related, to which she alone possesses the key. 



The question of continuity or discontinuity is not, however, one 

 of these. It is true that some groups of organisms, such as 

 Brachiopods and Ammonites, seem to afford, in certain cases, 

 •evidence of continuous variation : on the other hand, instances 

 are known, which superficially considered might be claimed as 

 evidence of discontinuous variation or saltation ; but these are 

 realty ambiguous, since the imperfection of the record affords an 

 alternative explanation. This imperfection of the record is not 

 merely a phrase invented by Darwin. Its existence is unfortu- 

 nately only too real. Numerous, indeed, are the breaches in the 

 continuity of ancentrai series : Gaskell 2 and Steinmann 3 would 

 bridge them over by methods which it is for zoologists to consider; 

 the geologist will attribute them to imperfections in the record. 



The subject on which geology can speak with authority concerns 

 the relative rate of change by which organic transformation has 

 beeu effected. Some organisms maintain their characters with 

 such persistence throughout long periods of recorded time that 

 they may fairly be distinguished as stable ; others pass from one 



1 On this and related questions light may be expected from the important 

 investigations now being conducted by Prof. Bateson and bis school. 



2 Gaskell, 'The Origin of the Vertebrates' London, 1908. It is impossible 

 to refuse a tribute of admiration to this remarkable work. Whatever differ- 

 ence of opinion may exist on the general question, there can be none as to the 

 value of the observations or the importance of the arguments which the Author 

 marshals in support of his views. 



3 Gr. Steinmann, 'Die geologischen Grundlagen der Abstammungslehre ' 

 Leipzig, 1908 (284 pp.). 



