334 Reports & Proceedings — Geologists' Association. 



tributaries from what are now Northern Scotland and Scandinavia, 

 debouching somewhere off the north-east coast of England, the 

 deltaic material of which (now consolidated) forms the Millstone Grit. 



II. — Geologists' Association. 



June 6, 1919.— Mr. J. F. N. Green, E.A., E.G.S., President, in the 



Chair. 



The following paper was read: "Old Age and Extinction in 

 Fossils.". By W. D. Lang, Sc.D., E.G.S. 



I. A Biological view-point. 



The phenomena of old age and extinction must affect our general 

 biological views; and these, in turn, are reflected in our attitude 

 towards these phenomena. Yitalistic (or automatic) and mechanistic 

 (or environmental) views are contrasted, and emphasis laid on the 

 former. An organism has tendencies, or potentialities, towards 

 developing in definite and not in haphazard directions ; and these 

 tendencies become actualized during evolution. They are kept in 

 check by inhibiting factors, and on the removal of an inhibition there 

 is an outburst of evolutionary activity ; thus evolution is seen to be 

 periodic. Potentialities tend to become exhausted on actualization ; 

 but, before this happens, may lead to the exaggeration of a character 

 which, in turn, may cause the extinction of a lineage. Homceo- 

 morphy is the expression of common tendencies or potentialities 

 becoming actual along many divergent lineages. 



II. This view reflected on to the phenomena of old age and 



extinction in («) Cretaceous cribrimorph Polyzoa ; (b) 

 Ammonites ; and {c) llugose Corals. 



III. The consequences of this view. 



A view which ignores, or at least slights, environmental influences 

 is likely to overlook the truth in one direction as far as (so the author 

 believes) a purely environmental or mechanistic view, such as 

 orthodox Darwinism, overlooks it on the other side. As an organism 

 is a synthesis of structure and function, so its structure is a synthesis 

 of expression and impression — expression of potentialities and 

 impression of the environment. A synthesis is not an aggregate, for 

 it transcends the sum of its components. A transcendental theory of 

 evolution would link the field of philosophical biology to the realm 

 of general philosophy. 



COERESPONDEITCE. 



RECENT PAPERS ON THE DURHAM COALFIELD. 

 Sir, — In the Geological Magazine of April last (p. 163) 

 I observed a paper by Dr. D. Woolacott relating to the above 

 Coalfield, where he writes of " the little-known Ganister Series " of 

 that district, and I wondered what might be the precise meaning 

 he wished to convey by those words. Three or four coal-seams 

 belonging to that Series (i.e. below the Brockwell Seam) have been 

 vigorously worked for the past thirty years or more. The measures 



