QQ GENERAL EVOLUTION. 



8. The Coreopsis discoidea T. and (r., var. anomala, Gray, is, 

 according to Mr. Aubrey Smith, much more nearly allied to Bid- 

 ens fro7idosa than to other species of its own genus, and the latter 

 is nearer to it than to other species of Bidens. It differs chiefly, 

 if not altogether, in the generic character : the barbs of the ache- 

 nia are directed upward ; those of the Bidens downward. 



From these and many other such instances it may be derived : 

 That the nearest species of adjacent genera are more nearly allied 

 in specific characters than the most diverse species of the same 

 genus. 



9. While Taxodium distichum and Glyptostrolus europcens, 

 conifers of North America and of Eastern Asia, respectively, are 

 readily distinguished by generic peculiarities of their cones, in 

 specific characters they appear to be identical.* 



Confirmatory of this proposition is the statement of Parker : f 

 *^In tracing out the almost infinite varieties of the modifications 

 of any one specific type of shelled Rhizojood, my friend Prof. 

 Rupert Jones and I found that like varieties of distinct species are 

 much nearer in shape and appearance than unlike varieties of the 

 same essential species." (It is not unlikely that species should 

 here be read genus and variety species, though the latter may not 

 fulfill the requirements in regard to distinctiveness observed 

 among higher animals. In types like the Rhizopod, forms of this 

 grade may not be really differentiated. Their enormous geo- 

 graphical range would suggest this, if nothing else. ) 



Objection. — A class of objectors to the preceding explanation 

 of the relations in question will ascribe them to hybridization. 

 They have already done so to considerable extent among the 

 Teleosts (see the writings of von Siebold, Steindachner, and 

 Giinther). That hybrids exist in nature will be denied by none, 

 but that they are usual or abundant is not a probable condition of 

 a creation regulated by such order as ours is. The tendency to 

 modify in given lines of generic series, if admitted, will account 

 for many of the cases regarded as hybrids by the above authors, 

 for it is to be remarked in many cases how the generic characters 



during which they lived may have seen a change from forest to praii'ie. (It is not 

 intended to suggest that the species of the two genera arc necessarily of the same 

 or any given number.) 



* See Meehan, " Proc. Amer. Ass. Adv. Sci.," 1868. Newberry, " Ann. Lye," 

 N. Y., 1868. 



f " Transac. Zool. Soc.,'' London, 1864, p. 151. 



