CHAPTER XXV 



THE ORIGIN OF SPECIES AND GENERA 



Our ignorance of first causes Two hypotheses: slow and abrupt 

 variation Slowness of the direct or normal evolution Diver- 

 gence through geographical isolation Abrupt variation or 

 saltation of de Vries Its application to fossil animals Con- 

 clusions. 



WE now approach one of the most important prob- 

 lems set before us, that of the origin of species and 

 genera during the course of the palaeontological 

 history of the earth. I shall not here go in detail 

 into the oft-renewed discussion on the first causes 

 of the variations which have happened to beings, 

 living and fossil ; that is to say, on the formation 

 of new species. Are we, with Lamarck, Herbert 

 Spencer, Roux, Cope, Osborn, Hyatt, and the 

 whole of the modern neo-Lamarckian school, 

 to seek the cause of these changes in an active 

 mechanical strain of organisms, or in the effort 

 of beings towards an adaptation as perfect as 

 possible to the conditions of their environment ? 

 Or shall we look for it with Isidore Geoffroy- 

 Saint-Hilaire, Semper, Clessin, Locard, Dall, Schman- 

 kewitz, etc., in a direct and passive action of the 

 floating environment on the organs of animals, 

 and, in the end, on their general structure ? Ought 

 we, with Darwin, Wallace, Huxley, Haeckel, and all 



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