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THE GEOLOGICAL EVIDENCES OF EVOLUTION 
409 
exhibits a steady progression from lower to higher types, 
excepting only the deficiency in the bird record which is 
easily explained. The comparative perfection of type in 
which each of these classes first appears, renders it certain that 
the origin of each and all of them must be sought much 
farther back than any records which have yet been discovered. 
The researches of palaeontologists and embryologists indicate 
a reptilian origin for birds and mammals, while reptiles and 
amphibia arose, perhaps independently, from fishes. 
Concluding Remarks. 
The brief review we have now taken of the more suggestive 
facts presented by the geological succession of organic forms, 
is sufficient to show that most, if not all, of the supposed 
difficulties which it presents in the way of evolution, are due 
either to imperfections in the geological record itself, or to our 
still very incomplete knowledge of what is really recorded in 
the earth’s crust. We learn, however, that just as discovery 
progresses, gaps are filled up and difficulties disappear; while, 
in the case of many individual groups, we have already 
obtained all the evidence of progressive development that can 
reasonably be expected. We conclude, therefore, that the 
geological difficulty has now disappeared : and that this noble 
science, when properly understood, affords clear and weighty 
evidence of evolution. 
