CHAPTER III.

Lamarck's Theory of Progression illustrated.--Class of Facts which give Color to it.--The Credulity of _Unbelief_.--M. Maillet and his Fish-birds.--Gradation not Progress.--Geological Argument.--The Present incomplete without the Past.--Intermediate Links of Creation.--Organisms of the Lower Old Red Sandstone.--The _Pterichthys_.--Its first Discovery.--Mr. Murchison's Decision regarding it.--Confirmed by that of Agassiz.--Description.--The several Varieties of the Fossil yet discovered.--Evidence of violent Death in the Attitudes in which they are found.--The Coccosteus of the Lower Old Red.--Description.--Gradations from Crustacea to Fishes.--Habits of the _Coccosteus_.--Scarcely any Conception too extravagant for Nature to realize, 35-54