chap, iv.] EVOLUTION THE KEY TO DISTRIBUTION. 
69 
different groups of animals, were such as would have enabled 
all the now disconnected groups to have once formed parts of a 
continuous series. Proofs of such former continuity are con- 
tinually being obtained by the discovery of allied extinct forms 
in intervening lands, but the extreme imperfection of the 
geological record as regards land animals renders it unlikely 
that this proof will be forthcoming in the majority of cases. 
The notion that if such animals ever existed their remains 
would certainly be found, is a superstition which, notwith- 
standing the efforts of Lyell and Darwin, still largely prevails 
among naturalists ; but until it is got rid of no true notions of 
the former distribution of life upon the earth can be attained. 
