Survival of the Fittest. 443 
occurred in nature and have been preserved and accumulated 
by Natural Selection, and not in the ordinary view of inde- 
pendent creation, we can understand why the specific charac- 
ters, or those by which the species of the same genus differ 
from each other, should be more variable than the generic 
characters in which they all agree. Inexplicable as is the 
occasional appearance of stripes on the shoulders and legs of 
the different equine species and their hybrids on the theory 
of creation, yet how simply is the fact explained if we believe 
that they are all descended from a striped progenitor just as 
the different domestic breeds of pigeons are descended from 
the blue and barred rock-pigeons. Why, for example, 
should the color of a flower be more likely to vary in any 
one species of a genus, if the other species, supposed to have 
been created independently, have differently-colored flowers, 
than if all the species of the genus have the same colored 
flowers? On the theory that species are only well-marked 
varieties, of which the characters have beccme in a high 
degree permanent, the fact is intelligible, for they have 
already varied in certain characters since they branched off 
from a common progenitor, and by these characters they 
have come to be specifically distinct from each other. There- 
fore, these same characters would be more likely again to 
vary than the generic characters which have been inherited 
without change for an enormous period of time. 
Upon the theory of Natural Selection, or the Survival of 
the Fittest, with its contingencies of extinction and diver- 
gence of character, we can see how it is that all past and 
present organic beings can be arranged within a few classes, 
in groups subordinate to groups, and with the extinct groups 
often falling in between the recent groups. We can see how 
it is that the mutual affinities of the forms within each class 
are so complex and diversified, and only adaptive characters, 
though of superior importance to the beings, are of scarcely 
any significance in classification, while those derived from 
rudimentary parts, though of no recognized service, are often 
