DISTRIBUTION. 323 



To form a conception of the total amount and general 

 direction of the change that has arisen in organic forms during 

 the geologic time measured by our sedimentary series, is at 

 present impossible — the data are insufficient. The immense 

 contrast between the few and low forms of the earliest-known 

 Fauna, and the many and high forms of our existing Fauna, 

 has been commonly supposed to prove, not only great 

 change but great progress. Nevertheless, this appearance 

 of progress may be, and probably is, mainly illusive. 

 Wider knowledge and increased power of interpretation, have 

 made it manifest that remains of comparatively well- organized 

 creatures, really existed in strata long supposed to be devoid 

 of them ; and that where they are actually absent, the nature 

 of the strata often supplies a sufficient explanation of their 

 absence, without assuming that they did not exist when these 

 strata were formed. It has now become a tenable hypothesis, 

 that the successively-higher types fossilized in our successive- 

 ly-later deposits, indicate nothing more than successive migra- 

 tions from pre-existing continents, to continents that were 

 step by step emerging from the ocean — migrations which 

 necessarily began with the inferior orders of organisms, and 

 included the successively-superior orders as the new lands 

 became more accessible to them, and better fitted for them.* 



While the evidence usually supposed to prove progres- 

 sion, is thus untrustworthy, there is trustworthy evidence 

 that there has been, in many cases, little or no progression. 

 Though the types which have existed from palaeozoic and me- 

 eozoic times down to the present day, are almost universally 

 changed ; yet a comparison of ancient and modern members 

 of these types, shows that the total amount of change is not 

 relatively great, and that it is not manifestly towards a higher 

 organization. Though nearly all the living forms which have 

 prototypes in early formations, differ from these prototypes 

 specifically, and in most cases generically ; yet ordinal pecu- 

 liarities are, in very numerous cases, maintained from the earli- 

 * For explanations, see "Illogical Geology." Essays : Second Series. 



