POSTSCRIPT. 527 



their standard or average types, arising out of some 

 slight changes in some of the ten million individuals, 

 which go to form the average. — 3. It may perchance take 

 ten thousand years to operate a change in the average 

 type of any species, equal to the difference between two 

 species. 



These slow changes in the average types would be 

 inappreciable to mankind under past and present con- 

 ditions of scientific record. — They would not require 

 individual changes so great or rapid as those which are 

 actually observed any year in the occurrence of varieties. 

 — And yet they would suffice to alter the whole flora and 

 fauna of the earth at the ra,te proposed by Lyell, as being 

 adequate to account for the facts ascertained. 



Thames Dillon — Kingston — Surrey. 

 April, 1859. 



t. NEWMAN, nUNTEE, DEVONSHIIIE STREET, BISHOPSOAlE, LONDOK. 



