356 SECTIONAL TRANSACTIONS. — C. 



related forms calls for graxlual successional changes in. the 

 same direction as regards any particular structure (ortho- 

 genesis). Mendelian experiments do not yet afford any great 

 support for either of these demands. Observed mutational 

 changes do not call for environmental influence, and are 

 ■wholly apart from any adaptive considerations ; natural 

 selection plays no part in the origin or preservation of 

 variations, but may be eliminative. It is highly questionable 

 whether somatic or environmental influences can modify the 

 germinal factors in definite directions, but disruptive changes 

 and gradual loss of factorial vigour, or perhaps senility, may 

 be contemplated, continued over long ages. As the common 

 germ plasm of a race may at any one time be presumed to be 

 in somewhat the same condition, evolutionary changes on 

 somewhat similar lines may be expected. 



Prof. A. Dendy, F.E.S. 



Thursday, August 26. 



6. Dr. T. Feanklin Sibly. — The Old Red Sandstone of the 



Mitcheldean Disirict, Gloucestershire . 



Mitcheldean lies on the Gloucestershire-Herefordshire 

 border ten miles west of Gloucester, and in the latitude of 

 the Breconshire Beacons. In this neighbourhood persistent 

 westerly dips determine an outcrop of the whole of the 

 Old Red iSandstone, with a thickness of some 7,500 feet, in a 

 band scarcely two miles wide, bounded on the east iby the 

 Silurian strata of the May Hill anticline and on the west by 

 the Carboniferous of the Forest of Dean coal-basin. The 

 sequence of strata determined in this locality offers a possible 

 key to the wilderness of Old Red Sandstone in Herefordshire. 



7. Prof. W. M. Flinders Peteie, F.R.S. — The Continuance 



of Life on the Earth. 



If by any process of aggregation the earth has been at a 

 red heat, all the lime and soda would be combined with the 

 silica (now sandstone) and all the carbonic and hydrochloric 

 acids would be in the atmosphere (now locked up in limestone 

 and salt). The changes from that condition would consist in 

 the acids gradually decomposing the silicates ; at present 

 there is only a minute fraction of the original carbonic acid 

 left in the atmosphere. The decomposition of a few more 

 inches of silicates over the globe would exhaust the carbonic 

 acid, and life could not exist. This may take place in a 

 few hundred thousand years, and such is the limit to 

 vegetable and therefore to animal life, irrespective of solar 

 cooling. The amount of carbon in the strata is probably 

 enough to combine with all the oxygen of the air ; hence land- 

 breathing animals were impossible until after the carbon 

 had become .separated and left oxygen free. This agrees 

 with the appearance of air breathers after the Carboniferous 

 age. 



8. Dr. A. E. Trueman. — The Liassic Rocks of Somerset- 



shire and their Correlation. 



The Liassic locks of Somerset are thin but richly fossili- 

 fei'ou.s, yielding many large Ammonites. When followed 

 towards the Mendips there is considerable reduction in 

 thickness and marked lithological change. At several 

 localities a white limestone resembling the Sutton Stone of 

 Glamorgan is seen to rest on the Carboniferous Limestone ; 



