were present in the immediately preceding generations; but characters
sometimes reappear in the same manner after a much longer interval of time.
Thus the calves of a hornless race of cattle which originated in Corrientes,
though at first quite hornless, as they become adult sometimes acquire small,
crooked, and loose horns; and these in succeeding years occasionally become
attached to the skull. (13/25. Azara 'Essais Hist. Nat. de Paraguay' tome 2
1801 page 372.) White and black Bantams, both of which generally breed true,
sometimes assume as they grow old a saffron or red plumage. For instance, a
first-rate black bantam has been described, which during three seasons was
perfectly black, but then annually became more and more red; and it deserves
notice that this tendency to change, whenever it occurs in a bantam, "is
almost certain to prove hereditary." (13/26. These facts are given on the high
authority of Mr. Hewitt in 'The Poultry Book' by Mr. Tegetmeier 1866 page
248.) The cuckoo or blue-mottled Dorking cock, when old, is liable to acquire
yellow or orange hackles in place of his proper bluish-grey hackles. (13/27.
'The Poultry Book' by Tegetmeier 1866 page 97.) Now as Gallus bankiva is
coloured red and orange, and as Dorking fowls and bantams are descended from
this species, we can hardly doubt that the change which occasionally occurs in
the plumage of these birds as their age advances, results from a tendency in
the individual to revert to the primitive type.

CROSSING AS A DIRECT CAUSE OF REVERSION.

It has long been notorious that hybrids and mongrels often revert to both or
to one of their parent-forms, after an interval of from two to seven or eight,
or, according to some authorities, even a greater number of generations. But
that the act of crossing in itself gives an impulse towards reversion, as
shown by the reappearance of long-lost characters, has never, I believe, been
hitherto proved. The proof lies in certain peculiarities, which do not
characterise the immediate parents, and therefore cannot have been derived