SECTION D.— ZOOLOGY. 



THE ANCIENT HISTORY OF SPONGES 

 AND ANIMALS. 



ADDRESS BY 



G. P. BIDDER, Sc.D., 



PRESIDENT OF THE SECTION. 



Among animals, man alone knows of a past and hopes for a future. Our 

 life is still delightful, because still we do not know what will happen an 

 hour from now ; but as the intellectual development of man has increased, 

 so has he lengthened his conscious past. 



The Cambrian, as the lowest of our fossiliferous rocks, used to be con- 

 sidered the limit of life. With masterly insight Darwin concluded, on 

 purely evolutionary grounds, that living things were on the earth for 

 as long a time before the Cambrian epoch as they have been since. Huxley 

 and Poulton — two great names in our history — showed that such a time 

 must be measured by the hundred million of years. They maintained, 

 against the full strength of Section A, the power of biology and geology 

 to prove the important physical fact, that for hundreds of millions of years 

 the world had been cool enough for habitation. 



The past has lengthened now for mathematicians ; they have enriched 

 us with the time-scale of radio-activity, and proved Darwin, Huxley and 

 Poulton to have been right. They show that the ocean has existed for 

 more than 1000 million years at a habitable temperature, and promise us 

 the great boon of a date for every geological formation. We may 

 gather from Jeffreys 1 and Holmes 2 that the constants for the time-scale of 

 the age of rocks are rapidly approaching certainty, but that the constants 

 of the lunar theory and the knowledge of geophysics and palaeogeography 

 are not yet sufficiently ascertained to determine the height of tides in the 

 sea five hundred or a thousand million years ago. 



I wish to draw your attention to the great denudation just before the 

 Cambrian, and to biological indications that it was produced by a period 

 of gigantic tides, on such a cataclysmic scale as gravely to interrupt the 

 sequence of evolution. 



Beneath the Cambrian in Scotland is the Torridonian sandstone, in 

 which Geikie 3 describes some two miles thick of peacefully bedded sand- 

 stones, with shales and sea-beaches, deposited over an old land-surface of 



1 ' The Earth.' Cambridge, 1924, University Press. 



2 ' The Age of the Earth.' London, 1927, Ernest Benn. (Price Gd., and worth 

 a guinea !) 



3 Text-book of Geology. Vol. ii, pp. 877, 891, S92. London, 1903, Macinillan. 



