place. Once moulted, the peculiarity has ceased. Of course all the birds
emanating from this stock have black wings and tails the first year." (14/33.
Kidd 'Treatise on the Canary' page 18.) A curious and somewhat analogous
account has been given (14/34. Charlesworth 'Mag. of Nat. Hist.' volume 1 1837
page 167.) of a family of wild pied rooks which were first observed in 1798,
near Chalfont, and which every year from that date up to the period of the
published notice, viz., 1837 "have several of their brood particoloured, black
and white. This variegation of the plumage, however, disappears with the first
moult; but among the next young families there are always a few pied ones."
These changes of plumage, which are inherited at various corresponding periods
of life in the pigeon, canary-bird, and rook, are remarkable, because the
parent-species passes through no such change.

Inherited diseases afford evidence in some respects of less value than the
foregoing cases, because diseases are not necessarily connected with any
change in structure; but in other respects of more value, because the periods
have been more carefully observed. Certain diseases are communicated to the
child apparently by a process like inoculation, and the child is from the
first affected; such cases may be here passed over. Large classes of diseases
usually appear at certain ages, such as St. Vitus's dance in youth,
consumption in early mid-life, gout later, and apoplexy still later; and these
are naturally inherited at the same period. But even in diseases of this
class, instances have been recorded, as with St. Vitus's dance, showing that
an unusually early or late tendency to the disease is inheritable. (14/35. Dr.
Prosper Lucas 'Hered. Nat.' tome 2 page 713.) In most cases the appearance of
any inherited disease is largely determined by certain critical periods in
each person's life, as well as by unfavourable conditions. There are many
other diseases, which are not attached to any particular period, but which
certainly tend to appear in the child at about the same age at which the
parent was first attacked. An array of high authorities, ancient and modern,