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. 

 Professor Owen's view. Mr. "Wallace. Professor Huxley. Objec- 

 tions 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. Glyptodon. 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 insignificant and minute 

 whether fortuitous or not. 



Arguments may yet be advanced in favour 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 JEquus), 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 



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

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



