148 RESULTS OF THE ACTION OF [Chap. IT. 



The intermediate species, also (and this is a very 

 important consideration), which connected the original 

 species (A) and (I), have all become, excepting (F), 

 extinct, and have left no descendants. Hence the six 

 new species descended from (I), and the eight descen- 

 dants 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 more parent- 

 species are supposed to be descended from some one 

 species of an earlier genus. In our diagram, this is 

 indicated by the broken lines, beneath the capital letters, 

 converging in sub-branches downwards towards a single 

 point ; this point represents a species, the supposed pro- 

 genitor of our several new sub-genera and genera. 



It is worth while to reflect for a moment on the 

 character of the new species F 14 , which is supposed not 

 to have diverged much in character, but to have retained 

 the form of (F), either unaltered or altered only in a 

 slight degree. In this case, its affinities to the other 

 fourteen new species will be of a curious and circuitous 

 nature. Being descended from a form which stood 

 between the parent-species (A) and (I), now supposed 

 to be extinct and unknown, it will be in some degree 

 intermediate in character between the two grouj)s 

 descended from these two species. But as these two 

 groups have gone on diverging in character from the 

 type of their parents, the new species (f u ) will not be 

 directlv intermediate between them, but rather between 

 types of the two groups ; and every naturalist will be 

 able to call such cases before his mind. 



In the diagram, each horizontal line has hitherto been 



