IV.] MINUTE MODIFICATIONS. HI 



CHAPTER IV. 



MINUTE AND GRADUAL MODIFICATIONS. 



There are Difficulties as to Minute Modifications, even if not fortuitous. Examples of 

 Sudden and Considerable Modifications of Different Kinds. Prof. Owen's View. 

 Mr. Wallace. Prof. Huxley. Objections to Sudden Changes. Labyrinthodont 

 Potto. Cetacea. As to Origin of Bird's Wing. Tendrils of Climbing Plants. 

 Animals once supposed to be Connecting Links. Early Specialization of Structure. 

 Macrauchenia. Olyptodon. Sabre-toothed Tiger. Conclusion. 



NOT only are there good reasons against the acceptance 

 of the exclusive operation of " Natural Selection " as the 

 one means of specific origination, but there are difficulties 

 in the way of accounting for such origination by the sole 

 action of modifications which are infinitesimal and minute, 

 whether fortuitous or not. 



Arguments may yet be advanced in favor of the view 

 that new species have from time to time manifested them- 

 selves with suddenness, and by modifications appearing at 

 once (as great in degree as are those which separate Hip- 

 parion from Equus), the species remaining stable in the 

 intervals of such modifications : by stable being meant that 

 their variations only extend for a certain degree in various 

 directions, like oscillations in a stable equilibrium. This 

 is the conception of Mr. Galton, 1 who compares the devel- 

 opment of species with a many-facetted spheroid tumbling 

 over from one facet, or stable equilibrium, to another. The 

 existence of internal conditions in animals corresponding 



1 " Hereditary Genius, an Inquiry into its Laws," etc. By Francis 

 Galton, F. R. S. (London: Macmillan.) 



