PALEONTOLOGY, ITS AIMS AND METHOD 219 



or less accuracy) of a miscellaneous collection of fossils ceases 

 to be regarded as a necessary or indeed the essential function 

 of a palaeontologist. 



The view of the true method of using fossils as geological 

 time indicators developed in this essay leads to a justifiable 

 doubt of the value of plant evidence in the discussion of the 

 smaller divisions of geological time. With one exception no 

 phyletic series of fossil plants, even of the broadest nature, 

 has been established. Nothing whatever is known of the 

 evolutionary trend of any of the plants found so abundantly 

 as impressions in the rocks, and the number of independent 

 variables which can possibly be recognised in such material, 

 which alone can serve the purposes of geological work, is so 

 small that the separation of allied stocks would be almost 

 hopeless, even if phyletic trends could be established. 



It therefore seems essential for the further development 

 of the geological uses of fossils, as it is for their biological in- 

 terest, that palaeontologists should concentrate on the detailed 

 study of zoological groups, preferably of common fossils, with 

 the primary aim of discovering their true relations to one 

 another, that is, of producing phyletic diagrams. The family 

 histories so established will directly fill all the needs of the 

 geologist, who will have the unfamiliar sensation of using 

 evidence the nature and meaning of which he understands 

 and the probable value of which he will have data for esti- 

 mating. 



All the uses of palaeontology may thus be provided for by 

 a single comprehensive study, and that this study must be 

 founded on the recognition of the unique feature of palaeonto- 

 logical material, that the relative ages of its subjects are 

 known, is the only real foundation of its claim to distinction. 



