ft parts; it is believed by some authors that with birds the diversity
in the shape of the pelvis causes the remarkable diversity in the shape
of the kidneys. Others believe that the shape of the pelvis in the human
mother influences by pressure the shape of the head of the child. In
snakes, according to Schlegel, the shape of the body and the manner
of swallowing determine the position and form of several of the most
important viscera.

The nature of the bond is frequently quite obscure. M. Is. Geoffroy St.
Hilaire has forcibly remarked that certain malconformations frequently,
and that others rarely, coexist without our being able to assign any
reason. What can be more singular than the relation in cats between
complete whiteness and blue eyes with deafness, or between the
tortoise-shell colour and the female sex; or in pigeons, between their
feathered feet and skin betwixt the outer toes, or between the presence
of more or less down on the young pigeon when first hatched, with the
future colour of its plumage; or, again, the relation between the hair
and the teeth in the naked Turkish dog, though here no doubt homology
comes into play? With respect to this latter case of correlation, I
think it can hardly be accidental that the two orders of mammals which
are most abnormal in their dermal covering, viz., Cetacea (whales) and
Edentata (armadilloes, scaly ant-eaters, etc.), are likewise on the
whole the most abnormal in their teeth, but there are so many exceptions
to this rule, as Mr. Mivart has remarked, that it has little value.

I know of no case better adapted to show the importance of the laws of
correlation and variation, independently of utility, and therefore of
natural selection, than that of the difference between the outer and
inner flowers in some Compositous and Umbelliferous plants. Everyone is
familiar with the difference between the ray and central florets of, for
instance, the daisy, and this difference is often accompanied with the
partial or complete abortion of the reproductive organs. But in some
of these plants the seeds also differ in shape and sculpture. These
differences have sometimes been attributed to the pressure of the
involucra on the florets, or to their mutual pressure, and the shape of
the seeds in the ray-florets of some Compositae countenances this idea;
but with the Umbelliferae it is by no means, as Dr. Hooker informs me,
the species with the densest heads which most frequently di