e young are born most perfect are the highest, because
farthest from the low Marsupial type. This would make the Ruminants and
Ungulata higher than the Quadrumana or the Carnivora. But the Mammalia
offer a still more remarkable illustration of the fallacy of this mode
of reasoning, for if there is one character more than another which is
essential and distinctive of the class, it is that from which it derives
its name, the possession of mammary glands and the power of suckling
the young. What more reasonable, apparently, than to argue that the
group in which this important function is most developed, that in which
the young are most dependent upon it, and for the longest period, must
be the highest in the Mammalian scale of organization? Yet this group is
the Marsupial, in which the young commence suckling in a foetal
condition, and continue to do so till they are fully developed, and are
therefore for a long time absolutely dependent on this mode of
nourishment.

These examples, I think, demonstrate that we cannot settle the rank of a
group by a consideration of the degree in which certain characters
resemble or differ from those in what is admitted to be a lower group;
and they also show that the highest group of a class may be more closely
connected to one of the lowest, than some other groups which have
developed laterally and diverged farther from the parent type, but which
yet, owing to want of balance or too great specialization in their
structure, have never reached a high grade of organization. The
Quadrumana afford a very valuable illustration, because, owing to their
undoubted affinity with man, we feel certain that they are really higher
than any other order of Mammalia, while at the same time they are more
distinctly allied to the lowest groups than many others. The case of the
Papilionidae seems to me so exactly parallel to this, that, while I admit
all the proofs of affinity with the undoubtedly lower groups of
Hesperidae and moths, I yet maintain that, owing to the complete and
even development of every part of their organization, these insects best
represent the highest perfection to which the butterfly type has
attained, and deserve to be placed at its head in every system of
classification.

_Distribution of the Papilionidae._

The Papilionidae are pretty widely distributed over the earth, but are
especially abundant in the tropics, where they attain their maximum of
size and beauty, and the grea