But I must explain my meaning more fully. I believe that the arrangement of the groups within each class, in due subordination and relation to the other groups, must be strictly genealogical in order to be natural; but that the amount of differences in the several branches or groups, though allied in the same degree in blood to their common progenitor, may differ greatly, being due to the different degrees of modification which they have undergone; and this is expressed by the forms being ranked under different genera, families, sections, and orders.
The great objection against the account… is that he has not tried to distinguish more clearly between more or less primitive characters and therefore he has been unable to use the characters for tracing phylogeny.
Advocates of pure morphology continue to maintain that nothing – absolutely nothing whatsoever – occurs as a legitimate premise in an inference about the history of life on earth, other than shared attributes of individual specimens. Of course they are not consistent nor are they a monolithic faction. But to be consistent they have to make some very strong claims. They must exclude attributes that are predicated, not of organisms but of populations … They must rule out considerations of chorology (distribution in time and space), of function in the sense of how things work, and of such contextual information as niche and habitat. […]