… present writer has pointed out the probability that the aplacental condition of most Marsupials is actually primitive, and that the placental connection in Perameles, like a multitude of other characters in which Marsupials resemble Placentals, has been independently acquired; in other words, that it represents a convergent or homoplastic development.

However this may be, we have the more definite fact that the marsupials and Placentals are collateral and, in a certain sense, equivalent groups of common parentage; and this conception may be welcomed as clearing the way for a better perception of the details of their secondary evolution or adaptive radiation.

Importance of determining the order of appearance of diagnostic characters. – The relative age of different characters should in all cases be a primary object of research. The historical method (although open to many pitfalls) when judiciously applied seems more likely to lead to lasting phylogenetic results than the time honored method of setting down resemblances and differences between two animals…”.