148 RESULTS OP THE ACTION OF [Chap. IV. 



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 descendants 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^*, 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 be- 

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

 be extinct and unknown, it will be in some degree inter- 

 mediate in character between the two groups 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") will not be directly inter- 

 mediate between them, but rather between types of the 

 two groups; and every naturalist will be able to call such 

 eases before his mind. 



In the diagram, each horizontal line has hitherto 



