CHAPTER II 



Palaeontology and the Doctrine of Evolution. 



§ 1. TM Species. Its Variations.'^ 

 The profound change which Palaeontology has undergone 

 since the transformist ideas have been so almost universally 

 adopted, is due to two causes : On the one hand the doctrine of 

 Evolution has occasioned a very rapid progress in the study of 

 fossils, and on the other this study has supplied new arguments 

 in support of the new doctrine, whose upholders are naturally 

 led to push pal^ontologic researches farther and farther. We 

 have now, therefore, to point out how the fundamental principles 

 of the theory of Evolution both receive confirmation from the 

 study of extinct forms, and also throw new light on the history 

 of the succession of these forms. The relations of Palaeontology 

 to the study of the Variations of forms will then be the subject 

 of this chapter. 



Definition of species. — The definition of species is founded on 

 current observation made in all countries, of the evident resem- 

 blance of certain forms among themselves and the marked dif- 

 ferences between them and forms most closely allied to them. 

 Up to the time of Lamarck, it was held that a species was an 

 immutable entity^ limited by an absolute law. The clearest defi- 

 nition was that of Cuvier: "A species is an assemblage of all 

 organized creatures which have descended one from another 

 or from common ancestors and of all those which resemble them 

 as closely as they resemble each other." 



In treatises on Zoology and Botany details may be found 

 relating to the difficulty encountered in giving precision to these 

 definitions and in applying them to living creatures. Works on 

 Zoologic Philosophy discuss also the various criterions proposed, 

 such as the fecundity of hybrids, etc. 



* E. Perrrier, Traite cle Zool. fasc 1, 1890 Wallace, Darwinism, ch. VII. Huxley, E^uoZw- 

 tion in Brit. Encycl. vol. VIII, ani Evolution and the Origin of Species. Geddes, Variation, 

 idem vol. XXIV. 



