Classification, 45 
ment of group subordinate to group, when duc 
tegard is paid to degrees of anatomical resemblance 
—this mere fact of itself tells so weightily in favour 
of descent with progressive modification in different 
lines, that even if it stood alone it would be entitled 
to rank as one of our strongest pieces of evidence. 
But, as we have seen, it does not stand alone. When 
we look beyond this large and general fact of all the 
innumerable forms of life being thus united in a 
tree-like system by an unquestionable relationship of 
some kind, to those smaller details in the science of 
classification which have been found most useful as 
guides for this kind of research, then we find that all 
these details, or empirically discovered rules, are 
exactly what we should have expected them to be, 
supposing the real meaning of classification to have 
been that of tracing lines of pedigree. 
In particular, we have seen that the most archaic 
types are both simpler in their organization and more 
generalized in their characters than are the more 
recent types—a fact of which no explanation can be 
given on the theory of special creation. But, upon the 
theory of natural evolution, we can without difficulty 
understand why the earlier forms should have been 
the simpler forms, and also why they should have 
been the most generalized. For it is out of the older 
forms that the newer must have grown; and, as they 
multiplied. they must have become more and more 
differentiated. 
Again, we have seen that there is no correlation 
between the importance of any structure from a 
classificatory point of view, and the importance of that 
structure to the organism which presents it. On the 
