166 THOUGHTS ON SPECIES. 



nation of species from the characters of the perfect being, 

 must be left to future investigation. 



Since the above was written, my friend Dr. John L. 

 Le Conte, of Philadelphia, has suggested an important con- 

 sideration, which should not be forgotten by those who may 

 attempt to investigate this subject. If hybridity is capable 

 of giving rise to a permanent variety, or seriously com- 

 plicating the determination of species, such intermixture has 

 most probably already taken place, in species of the same geo- 

 graphical distribution, to a degree that has exhausted the 

 capability of further intermixture. For it seems most im- 

 probable to suppose that species, capable of producing per- 

 manent intermediate forms by crossing, could be associated 

 together for indefinite periods of time in the same area, and 

 not have had the tendency called into activity long since by 

 the production of permanent hybrids, now indistinguishable 

 and registered as true species. Hence, if there be anything 

 of truth in a supposition so probable, it is easy to perceive 

 why the hybrid is incapable of propagating with its own 

 kind, and why in mixing with the parent stock there is a 

 constant tendency to revert to it. 



To arrive at any satisfactory solution of the question, 

 however, it will be necessary to determine the effect of the 

 intermixture of closely allied but distinct species from widely 

 separated countries. 



In order to make the foregoing ideas respecting species as 

 clear and definite as possible, it may be well, perhaps, to 

 throw them into the form of a definition. It may be 

 regarded, therefore, as a specific cycle of organic and in- 

 stinctive actions, manifested in the production of repre- 

 sentative forms and in their biographies, having reference 



