Chap. IV. DIVEEGENCE OF CHAKACTEE. 123 



The new species in our diagram descended from the 

 original eleven species, will now be fifteen in number. 

 Owing to the divergent tendency of natural selection, 

 the extreme amount of difference in character between 

 species a u and z 14 will be much greater than that 

 between the most different of the original eleven species. 

 The new species, moreover, will be allied to each other 

 in a widely different manner. Of the eight descendants 

 from (A) the three marked a 14 , q li , p u , will be nearly 

 related from having recently branched off from a 10 ; b 14 

 and / 14 , from having diverged at an earlier period from 

 a 5 , will be in some degree distinct from the three first- 

 named species ; and lastly, o w , e I4 , and m 14 , will be 

 nearly related one to the other, but from having di- 

 verged at the first commencement of the process of 

 modification, will be widely different from the other 

 five species, and may constitute a sub-genus or even a 

 distinct genus. 



The six descendants from (I) will form two sub- 

 genera or even genera. But as the original species (I) 

 differed largely from (A), standing nearly at the extreme 

 points of the original genus, the six descendants from 

 (I) will, owing to inheritance, differ considerably from 

 the eight descendants from (A) ; the two groups, more- 

 over, are supposed to have gone on diverging in dif- 

 ferent directions. The intermediate species, also (and 

 this is a very important consideration), which connected 

 the original species (A) and (I), have all become, ex- 

 cepting (F), extinct, and have left no descendants. 

 Hence the six new species descended from (I), and the 

 eight descended from (A), will have to be ranked as 

 very distinct genera, or even as distinct sub-families. 



Thus it is, as I believe, that two or more genera 

 are produced by descent, with modification, from two 

 or more species of the same genus. And the two or 



G2 



