cases of reversion effected by means of buds, and therefore independent of
true or seminal generation. Perhaps even a fourth class might be instituted,
to include reversions by segments in the same individual flower or fruit, and
in different parts of the body in the same individual animal as it grows old.
But the two first main classes will be sufficient for our purpose.

REVERSION TO LOST CHARACTERS BY PURE OR UNCROSSED FORMS.

Striking instances of this first class of cases were given in the sixth
chapter, namely, of the occasional reappearance, in variously-coloured breeds
of the pigeon, of blue birds with all the marks characteristic of the wild
Columba livia. Similar cases were given in the case of the fowl. With the
common ass, as the legs of the wild progenitor are almost always striped, we
may feel assured that the occasional appearance of such stripes in the
domestic animal is a case of simple reversion. But I shall be compelled to
refer again to these cases, and therefore here pass them over.

The aboriginal species from which our domesticated cattle and sheep are
descended, no doubt possessed horns; but several hornless breeds are now well
established. Yet in these--for instance, in Southdown sheep--"it is not
unusual to find among the male lambs some with small horns." The horns, which
thus occasionally reappear in other polled breeds, either "grow to the full
size," or are curiously attached to the skin alone and hang "loosely down, or
drop off." (13/1. 'Youatt on Sheep' pages 20, 234. The same fact of loose
horns occasionally appearing in hornless breeds has been observed in Germany;
Bechstein 'Naturgesch. Deutschlands.' b. 1 s. 362.) The Galloways and Suffolk
cattle have been hornless for the last 100 or 150 years, but a horned calf,
with the horn often loosely attached, is occasionally produced. (13/2. 'Youatt
on Cattle' pages 155, 174.)