86 Trans. Acad. Sci. of St. Louis. 



The study of palaeontology, a science which could hardly 

 be said to have been in existence a century ago, received the 

 same impetus from the doctrine of descent as did compara- 

 tive anatomy and embryology, and it has undergone a marvel- 

 ous development in our epoch. If the present fauna is the 

 last link in the long series of animal forms which have suc- 

 ceeded one another by slow and gradual substitution of 

 species, it is from an examination of the fossiliferous remains 

 that we should find the prima facie evidence of evolution. 

 Cuvier and his disciples, it is true, had already studied the 

 fossils of the Paris basin with rich results, but it was not 

 until after Darwin that the science entered upon its modern 

 development. Considering the difficulties that beset any 

 palaeontological investigation and the fact that only a few 

 spots in the earth's crust have been scratched for fossilifer- 

 ous remains, the achievements have been remarkable. Huxley 

 in England and the American school of palaeontologists, 

 notably Cope, Marsh, Osborn and Scott, have brought to light 

 a wealth of material, the western plains of the United States 

 alone yielding a world of extinct animal forms. The phy- 

 logenies of many animals have been discovered with greater 

 or less completeness, as for example, that of the horse, and 

 the proofs of organic evolution which palaeontology has 

 furnished have even surpassed expectation. 



II. EVOLUTION. 



Let us now turn to a consideration of the development of 

 evolutionary doctrines as applied to organic nature. 



The essence of the idea of the gradual development of 

 organisms can be traced back to the Greeks, for in the earliest 

 Ionians, Thales and Anaximander, more than six hundred 

 years before Christ, we find the first premonition of evolu- 

 tion. Later, in Heraclitus and Empedocles who set forth the 

 doctrine of the gradually increasing perfection of organisms, 

 the idea became somewhat less vague, the latter even dimly 

 foreshadowing the theory of the " Survival of the Fittest." 

 And still later we find in Aristotle very clearly brought forth 

 the principle of adaptation or fitness of certain structures to 



