CLASSIFICATION 235 



On the Nature of the Affinities connecting Organic Beings 



As the modified descendants of dominant species, 

 belonging to the larger genera, tend to inherit the 

 advantages which made the groups to which they be- 

 long large and their parents dominant, they are almost 

 sure to spread widely, and to seize on more and more 

 places in the economy of nature. The larger and more 

 dominant groups within each class thus tend to go on 

 increasing in size; and they consequently supplant many 

 smaller and feebler groups. Thus we can account for 

 the fact that all organisms, recent and extinct, are in- 

 cluded under a few great orders, and under still fewer 

 classes. As showing how few the higher groups are in 

 number, and how widely they are spread throughout 

 the world, the fact is striking that the discovery of Aus- 

 tralia has not added an insect belonging to a new class; 

 and that in the vegetable kingdom, as I learn from Dr. 

 Hooker, it has added only two or three families of small 

 size. 



In the chapter on Geological Succession I attempted 

 to show, on the principle of each group having generally 

 diverged much in character during the long-continued 

 process of modification, how it is that the more ancient 

 forms of life often present characters in some degree in- 

 termediate between existing groups. As some few of the 

 old and intermediate forms have transmitted to the pres- 

 ent day descendants but little modified, these constitute 

 our so-called osculant or aberrant species. The more 

 aberrant any form is, the greater must be the number 

 of connecting forms which have been exterminated and 

 utterly lost. And we have some evidence of aberrant 



