en. XL. BIOLOGY. 



419 



CHAPTER XL. 



SCIENCE OF THE NINETEENTH CENTURY (CONTINUED), 



Facts which led Naturalists to believe that the Different Kinds of 

 Animals are descended from Common Ancestors — All Animals 

 of each Class formed on one Plan— Embryologicai Structure- 

 Living and Fossil Animals of a Country resemble each other — 

 Gradual Succession of Animals on the Globe — Links between Dif- 

 ferent Species— Darwin's Theory of Natural Selection — Wallace 

 worked out th-e same Theory independently — Sketch of the Theory 

 of Natural Selection — Selection of Animals by Man — Selection by 

 Natural Causes — Difficulties in Natural History which are explained 

 by this Theory — Foolish Prejudices against it — Concluding Remarks 

 on the History of Science. 



Pacts wMoh liave led Naturalists to believe that the 

 different kinds of Animals are descended from common 

 Ancestors. — We now come to the first attempt of any value 

 which has ever been made, to explain how the different kinds 

 of animals and plants have been produced. This question 

 is so very difficult, and seems so much beyond our grasp, 

 that we find very i^^ people throughout the history of 

 science who even tried to answer it Aristotle, it is true, 

 remarked tliat we can trace such a close resemblance 

 between the different species, from the lowest plant up to 

 the highest animal, as would seem to show they are related 

 to each other (p. 16). Bonnet, too, thought that animals 

 were developed from lower into higher forms (p. 202) ; and 

 Lamarck, as we have seen, boldly suggested the same expla- 

 nation (p. 391). 



