XL] SPECIFIC GENESIS. 259 



these conditions have been exceptionally unchanging, 

 specific evolution may have been exceptionally rare. It 

 becomes then possible to suppose that for a similar period 

 stimuli to change in the manifestation of animal forms 

 may have been unusually few and feeble, that is, if the 

 conditions of the earth's orbit have been as exceptional 

 as stated. However, even if new species are now 

 being evolved as actively as ever, or if they have been so 

 quite recently, no conflict thence necessarily arises with 

 the view here advocated. For it by no means follows that 

 if some examples of new species have recently been sud- 

 denly produced from individuals of antecedent species, we 

 ought to be able to put our fingers on such cases ; as Mr. 

 Murphy well observes l in a passage before quoted, " If a 

 species were to come suddenly into being in a wild state, 

 as the Ancon sheep did under domestication, how could we 

 ascertain the fact ? If the first of a newly-born species 

 were found, the fact of its discovery would tell nothing 

 about its origin. Naturalists would register it as a very rare 

 species, having. been only once met with, but they would 

 have no means of knowing whether it were the first or the 

 last of its race." 



But are there any grounds for thinking that in the 

 genesis of species an internal force or tendency intervenes, 

 co-operating with and controlling the action of external 

 conditions ? 



It is here contended that there are such grounds, and 

 that though inheritance, reversion, atavism, Natural Selec- 

 tion, &c., play a part not unimportant, yet that such an 

 internal power is a great, perhaps the main, determin- 

 ing agent. 



1 "Habit and Intelligence," vol. i. p. 344. 



s2 



